Do not block subscribers until the unsubscription request to RPC server
is completed. Otherwise, another notification may be received from the
RPC server which will block the unsubscription process.
At the same time, fix event-based waiter. We must not block the receiver
channel during unsubscription because there's a chance that subsequent
event will be sent by the server. We need to read this event in order not
to block the WSClient's readloop.
v.estack is used throughout the code to work with estack, while ctx.sc.estack
is (theoretically) just a reference to it that is saved on script load and
restored to v.estack on context unload. The problem is that v.estack can grow
as we use it and can be reallocated away from its original slice (saved in the
ctx.sc.estack), so either ctx.sc.estack should be a pointer or we need to
ensure that it's correct when loading a new script. The second approach is a
bit safer for now and it fixes#2798.
And fix failing test along the way:
```
2022-11-11T12:37:47.0413934Z === RUN TestResetDB
2022-11-11T12:37:47.0414557Z 2022-11-11T12:36:54.510Z INFO initial gas supply is not set or wrong, setting default value {"InitialGASSupply": "52000000"}
2022-11-11T12:37:47.0415288Z 2022-11-11T12:36:54.510Z INFO MaxBlockSize is not set or wrong, setting default value {"MaxBlockSize": 262144}
2022-11-11T12:37:47.0416020Z 2022-11-11T12:36:54.510Z INFO MaxBlockSystemFee is not set or wrong, setting default value {"MaxBlockSystemFee": 900000000000}
2022-11-11T12:37:47.0416786Z 2022-11-11T12:36:54.510Z INFO MaxTransactionsPerBlock is not set or wrong, using default value {"MaxTransactionsPerBlock": 512}
2022-11-11T12:37:47.0417725Z 2022-11-11T12:36:54.510Z INFO MaxValidUntilBlockIncrement is not set or wrong, using default value {"MaxValidUntilBlockIncrement": 5760}
2022-11-11T12:37:47.0418415Z 2022-11-11T12:36:54.510Z INFO Hardforks are not set, using default value
2022-11-11T12:37:47.0419272Z 2022-11-11T12:36:54.523Z INFO no storage version found! creating genesis block
2022-11-11T12:37:47.0419997Z 2022-11-11T12:36:54.529Z INFO chain is already at the proper state {"height": 0}
2022-11-11T12:37:47.0420974Z testing.go:1097: TempDir RemoveAll cleanup: remove C:\Users\RUNNER~1\AppData\Local\Temp\TestResetDB671187463\001\chains\privnet\000001.log: The process cannot access the file because it is being used by another process.
2022-11-11T12:37:47.0421606Z --- FAIL: TestResetDB (1.99s)
```
client_test.go:1935:
Error Trace: /home/rik/dev/neo-go/pkg/services/rpcsrv/client_test.go:1935
Error: Should NOT be empty, but was 00000000-0000-0000-0000-000000000000
Test: TestClient_Iterator_SessionConfigVariations/sessions_disabled
It's obviously empty, since we have sessions disabled, but it was not
considered to be empty in testify 1.7.0, now it is, see 840cb80149
There is a security issue found in github.com/btcsuite/btcd that we don't care
about (we're only using 256k1 implementation), but GitHub complains about
it. We could update to github.com/btcsuite/btcd/btcec/v2, but it's now just a
thin wrapper over github.com/decred/dcrd/dcrec/secp256k1/v4, so we better use
it directly.
* strip NEP-XX methods before going into generator to avoid unused imports
* nepXX.Invoker types already include Call
* always import util, it's used for Hash
