rpc: add configuration extension for MPT-backed iterator sessions
Add ability to switch between current blockchain storage and MPT-backed
storage for iterator traversing process. It may be useful because
iterator implementation traverses underlying backed storage (BoltDB,
LevelDB) inside DB's Seek which is blocking operation for BoltDB:
```
Opening a read transaction and a write transaction in the same goroutine
can cause the writer to deadlock because the database periodically needs
to re-mmap itself as it grows and it cannot do that while a read transaction
is open.
If a long running read transaction (for example, a snapshot transaction)
is needed, you might want to set DB.InitialMmapSize to a large enough
value to avoid potential blocking of write transaction.
```
So during bbolt re-mmaping, standard blockchain DB operations (i.e. persist)
can be blocked until iterator resourses release. The described behaviour
is tested and confirmed on four-nodes privnet with BoltDB and
`SessionExpirationTime` set to be 180 seconds. After new iterator session
is added to the server, the subsequent persist took ~5m21s, see the log
record `2022-06-17T18:58:21.563+0300`:
```
anna@kiwi:~/Documents/GitProjects/nspcc-dev/neo-go$ ./bin/neo-go node -p
2022-06-17T18:52:21.535+0300 INFO initial gas supply is not set or wrong, setting default value {"InitialGASSupply": "52000000"}
2022-06-17T18:52:21.535+0300 INFO MaxBlockSize is not set or wrong, setting default value {"MaxBlockSize": 262144}
2022-06-17T18:52:21.535+0300 INFO MaxBlockSystemFee is not set or wrong, setting default value {"MaxBlockSystemFee": 900000000000}
2022-06-17T18:52:21.535+0300 INFO MaxTransactionsPerBlock is not set or wrong, using default value {"MaxTransactionsPerBlock": 512}
2022-06-17T18:52:21.535+0300 INFO MaxValidUntilBlockIncrement is not set or wrong, using default value {"MaxValidUntilBlockIncrement": 5760}
2022-06-17T18:52:21.535+0300 INFO Hardforks are not set, using default value
2022-06-17T18:52:21.543+0300 INFO no storage version found! creating genesis block
2022-06-17T18:52:21.546+0300 INFO ExtensiblePoolSize is not set or wrong, using default value {"ExtensiblePoolSize": 20}
2022-06-17T18:52:21.546+0300 INFO service is running {"service": "Prometheus", "endpoint": ":2112"}
2022-06-17T18:52:21.547+0300 INFO starting rpc-server {"endpoint": ":20331"}
2022-06-17T18:52:21.547+0300 INFO rpc-server iterator sessions are enabled
2022-06-17T18:52:21.547+0300 INFO service hasn't started since it's disabled {"service": "Pprof"}
2022-06-17T18:52:21.547+0300 INFO node started {"blockHeight": 0, "headerHeight": 0}
_ ____________ __________
/ | / / ____/ __ \ / ____/ __ \
/ |/ / __/ / / / /_____/ / __/ / / /
/ /| / /___/ /_/ /_____/ /_/ / /_/ /
/_/ |_/_____/\____/ \____/\____/
/NEO-GO:0.99.1-pre-53-g7ccb646e/
2022-06-17T18:52:21.548+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 1}
2022-06-17T18:52:21.550+0300 INFO started protocol {"addr": "127.0.0.1:20336", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 65, "id": 1475228436}
2022-06-17T18:52:22.575+0300 INFO persisted to disk {"blocks": 65, "keys": 1410, "headerHeight": 65, "blockHeight": 65, "took": "28.193409ms"}
2022-06-17T18:52:24.548+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 2}
2022-06-17T18:52:24.548+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 3}
2022-06-17T18:52:24.548+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 4}
2022-06-17T18:52:24.549+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 5}
2022-06-17T18:52:24.549+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 6}
2022-06-17T18:52:24.549+0300 INFO started protocol {"addr": "127.0.0.1:20333", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 65, "id": 3444438498}
2022-06-17T18:52:24.549+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 7}
2022-06-17T18:52:24.549+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 8}
2022-06-17T18:52:24.550+0300 INFO node reached synchronized state, starting services
2022-06-17T18:52:24.550+0300 INFO started protocol {"addr": "127.0.0.1:20334", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 65, "id": 2435677826}
2022-06-17T18:52:24.550+0300 INFO starting state validation service
2022-06-17T18:52:24.550+0300 INFO RPC server already started
2022-06-17T18:52:24.550+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 9}
2022-06-17T18:52:24.550+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 10}
2022-06-17T18:52:24.550+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "already connected", "peerCount": 9}
2022-06-17T18:52:24.550+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "already connected", "peerCount": 8}
2022-06-17T18:52:24.550+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "already connected", "peerCount": 7}
2022-06-17T18:52:24.550+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "unexpected empty payload: CMDVersion", "peerCount": 6}
2022-06-17T18:52:24.550+0300 INFO started protocol {"addr": "127.0.0.1:20335", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 65, "id": 970555896}
2022-06-17T18:52:24.551+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 7}
2022-06-17T18:52:24.551+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "unexpected empty payload: CMDVersion", "peerCount": 6}
2022-06-17T18:52:24.551+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "unexpected empty payload: CMDVersion", "peerCount": 5}
2022-06-17T18:52:24.551+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "already connected", "peerCount": 4}
2022-06-17T18:52:29.564+0300 INFO persisted to disk {"blocks": 1, "keys": 19, "headerHeight": 66, "blockHeight": 66, "took": "12.51808ms"}
2022-06-17T18:52:44.558+0300 INFO persisted to disk {"blocks": 1, "keys": 19, "headerHeight": 67, "blockHeight": 67, "took": "1.563137ms"}
2022-06-17T18:55:21.549+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "ping/pong timeout", "peerCount": 3}
2022-06-17T18:55:21.550+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "ping/pong timeout", "peerCount": 2}
2022-06-17T18:55:21.550+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "ping/pong timeout", "peerCount": 1}
2022-06-17T18:55:21.550+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "ping/pong timeout", "peerCount": 0}
2022-06-17T18:55:21.553+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 1}
2022-06-17T18:55:21.554+0300 INFO started protocol {"addr": "127.0.0.1:20335", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 77, "id": 970555896}
2022-06-17T18:55:24.554+0300 INFO new peer connected {"addr": "172.200.0.4:20333", "peerCount": 2}
2022-06-17T18:55:24.555+0300 INFO new peer connected {"addr": "172.200.0.3:20334", "peerCount": 3}
2022-06-17T18:55:24.555+0300 INFO new peer connected {"addr": "10.78.13.84:59876", "peerCount": 4}
2022-06-17T18:55:24.555+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 5}
2022-06-17T18:55:24.556+0300 INFO new peer connected {"addr": "172.200.0.254:20332", "peerCount": 6}
2022-06-17T18:55:24.556+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 7}
2022-06-17T18:55:24.556+0300 INFO started protocol {"addr": "172.200.0.4:20333", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 76, "id": 3444438498}
2022-06-17T18:55:24.556+0300 INFO new peer connected {"addr": "172.200.0.1:20335", "peerCount": 8}
2022-06-17T18:55:24.558+0300 INFO started protocol {"addr": "127.0.0.1:20336", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 77, "id": 1475228436}
2022-06-17T18:55:24.559+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 9}
2022-06-17T18:55:24.558+0300 INFO started protocol {"addr": "172.200.0.3:20334", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 77, "id": 2435677826}
2022-06-17T18:55:24.559+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 10}
2022-06-17T18:55:24.559+0300 WARN peer disconnected {"addr": "172.200.0.1:20335", "error": "unexpected empty payload: CMDVersion", "peerCount": 9}
2022-06-17T18:55:24.559+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 10}
2022-06-17T18:55:24.560+0300 INFO new peer connected {"addr": "172.200.0.2:20336", "peerCount": 11}
2022-06-17T18:55:24.560+0300 WARN peer disconnected {"addr": "172.200.0.254:20332", "error": "identical node id", "peerCount": 10}
2022-06-17T18:55:24.561+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "already connected", "peerCount": 9}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 10}
2022-06-17T18:55:24.561+0300 WARN peer disconnected {"addr": "10.78.13.84:59876", "error": "unexpected empty payload: CMDVersion", "peerCount": 9}
2022-06-17T18:55:24.561+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "already connected", "peerCount": 8}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 9}
2022-06-17T18:55:24.561+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "unexpected empty payload: CMDVersion", "peerCount": 8}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 9}
2022-06-17T18:55:24.561+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "unexpected empty payload: CMDVersion", "peerCount": 8}
2022-06-17T18:55:24.561+0300 WARN peer disconnected {"addr": "172.200.0.2:20336", "error": "unexpected empty payload: CMDVersion", "peerCount": 7}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 8}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 9}
2022-06-17T18:55:24.561+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "already connected", "peerCount": 8}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 9}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 10}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 11}
2022-06-17T18:55:24.561+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 12}
2022-06-17T18:55:24.562+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "already connected", "peerCount": 11}
2022-06-17T18:55:24.562+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 12}
2022-06-17T18:55:24.562+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 13}
2022-06-17T18:55:24.562+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "already connected", "peerCount": 12}
2022-06-17T18:55:24.562+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "already connected", "peerCount": 11}
2022-06-17T18:55:24.562+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "already connected", "peerCount": 10}
2022-06-17T18:55:24.562+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "unexpected empty payload: CMDVersion", "peerCount": 9}
2022-06-17T18:55:24.563+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 10}
2022-06-17T18:55:24.563+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "already connected", "peerCount": 9}
2022-06-17T18:55:24.563+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "unexpected empty payload: CMDVersion", "peerCount": 8}
2022-06-17T18:55:24.563+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "already connected", "peerCount": 7}
2022-06-17T18:55:24.563+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "max peers reached", "peerCount": 6}
2022-06-17T18:55:24.563+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "already connected", "peerCount": 5}
2022-06-17T18:55:24.563+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "max peers reached", "peerCount": 4}
2022-06-17T18:55:24.563+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "already connected", "peerCount": 3}
2022-06-17T18:57:21.551+0300 WARN peer disconnected {"addr": "172.200.0.4:20333", "error": "ping/pong timeout", "peerCount": 2}
2022-06-17T18:57:21.552+0300 WARN peer disconnected {"addr": "172.200.0.3:20334", "error": "ping/pong timeout", "peerCount": 1}
2022-06-17T18:57:21.552+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "ping/pong timeout", "peerCount": 0}
2022-06-17T18:57:21.553+0300 INFO new peer connected {"addr": "172.200.0.4:20333", "peerCount": 1}
2022-06-17T18:57:21.554+0300 INFO new peer connected {"addr": "10.78.13.84:20332", "peerCount": 2}
2022-06-17T18:57:21.555+0300 INFO started protocol {"addr": "172.200.0.4:20333", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 82, "id": 3444438498}
2022-06-17T18:57:21.556+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 3}
2022-06-17T18:57:21.556+0300 INFO new peer connected {"addr": "10.78.13.84:46076", "peerCount": 4}
2022-06-17T18:57:21.556+0300 INFO new peer connected {"addr": "172.200.0.1:20335", "peerCount": 5}
2022-06-17T18:57:21.556+0300 INFO new peer connected {"addr": "172.200.0.254:20332", "peerCount": 6}
2022-06-17T18:57:21.556+0300 INFO new peer connected {"addr": "10.78.13.84:59972", "peerCount": 7}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 8}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 9}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "172.200.0.2:20336", "peerCount": 10}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 11}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 12}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "172.200.0.3:20334", "peerCount": 13}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 14}
2022-06-17T18:57:21.557+0300 INFO started protocol {"addr": "127.0.0.1:20334", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 82, "id": 2435677826}
2022-06-17T18:57:21.557+0300 WARN peer disconnected {"addr": "172.200.0.2:20336", "error": "max peers reached", "peerCount": 13}
2022-06-17T18:57:21.557+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 14}
2022-06-17T18:57:21.558+0300 INFO started protocol {"addr": "172.200.0.1:20335", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 82, "id": 970555896}
2022-06-17T18:57:21.558+0300 WARN peer disconnected {"addr": "172.200.0.254:20332", "error": "identical node id", "peerCount": 13}
2022-06-17T18:57:21.558+0300 INFO new peer connected {"addr": "127.0.0.1:20334", "peerCount": 14}
2022-06-17T18:57:21.558+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "max peers reached", "peerCount": 13}
2022-06-17T18:57:21.558+0300 WARN peer disconnected {"addr": "10.78.13.84:46076", "error": "identical node id", "peerCount": 12}
2022-06-17T18:57:21.558+0300 INFO new peer connected {"addr": "127.0.0.1:20333", "peerCount": 13}
2022-06-17T18:57:21.558+0300 INFO new peer connected {"addr": "127.0.0.1:20335", "peerCount": 14}
2022-06-17T18:57:21.558+0300 INFO new peer connected {"addr": "127.0.0.1:20336", "peerCount": 15}
2022-06-17T18:57:21.558+0300 WARN peer disconnected {"addr": "10.78.13.84:59972", "error": "identical node id", "peerCount": 14}
2022-06-17T18:57:21.558+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "already connected", "peerCount": 13}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "10.78.13.84:20332", "error": "unexpected empty payload: CMDVersion", "peerCount": 12}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "already connected", "peerCount": 11}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "172.200.0.3:20334", "error": "unexpected empty payload: CMDVersion", "peerCount": 10}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "unexpected empty payload: CMDVersion", "peerCount": 9}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "127.0.0.1:20334", "error": "already connected", "peerCount": 8}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "unexpected empty payload: CMDVersion", "peerCount": 7}
2022-06-17T18:57:21.559+0300 INFO started protocol {"addr": "127.0.0.1:20336", "userAgent": "/NEO-GO:0.99.1-pre-53-g7ccb646e/", "startHeight": 82, "id": 1475228436}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "127.0.0.1:20333", "error": "already connected", "peerCount": 6}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "127.0.0.1:20335", "error": "already connected", "peerCount": 5}
2022-06-17T18:57:21.559+0300 WARN peer disconnected {"addr": "127.0.0.1:20336", "error": "already connected", "peerCount": 4}
2022-06-17T18:58:21.561+0300 INFO persisted to disk {"blocks": 1, "keys": 20, "headerHeight": 68, "blockHeight": 68, "took": "5m21.993873018s"}
2022-06-17T18:58:21.563+0300 INFO persisted to disk {"blocks": 8, "keys": 111, "headerHeight": 76, "blockHeight": 76, "took": "2.243347ms"}
2022-06-17T18:58:22.567+0300 INFO persisted to disk {"blocks": 10, "keys": 135, "headerHeight": 86, "blockHeight": 86, "took": "5.637669ms"}
2022-06-17T18:58:25.565+0300 INFO persisted to disk {"blocks": 1, "keys": 19, "headerHeight": 87, "blockHeight": 87, "took": "1.879912ms"}
2022-06-17T18:58:40.572+0300 INFO persisted to disk {"blocks": 1, "keys": 20, "headerHeight": 88, "blockHeight": 88, "took": "1.560317ms"}
2022-06-17T18:58:55.579+0300 INFO persisted to disk {"blocks": 1, "keys": 19, "headerHeight": 89, "blockHeight": 89, "took": "1.925225ms"}
2022-06-17T18:59:10.587+0300 INFO persisted to disk {"blocks": 1, "keys": 19, "headerHeight": 90, "blockHeight": 90, "took": "3.118073ms"}
2022-06-17T18:59:25.592+0300 INFO persisted to disk {"blocks": 1, "keys": 19, "headerHeight": 91, "blockHeight": 91, "took": "1.607248ms"}
2022-06-17T18:59:40.600+0300 INFO persisted to disk {"blocks": 1, "keys": 20, "headerHeight": 92, "blockHeight": 92, "took": "931.806µs"}
2022-06-17T18:59:55.610+0300 INFO persisted to disk {"blocks": 1, "keys": 19, "headerHeight": 93, "blockHeight": 93, "took": "2.019041ms"}
```
b5d39a3ffd