In 121c9664b we should take into account isValid flag of
NativePolicy contract while retrieving MaxVerificationGas native
policy value. Otherwise we won't be able to get MaxVerificationGas
after the node was restarted, because this value is not truly
stored along with the other native policy values.
This commit fixes bug with headers verification after the node
restarting with an existing storage:
```
2020-08-03T12:52:56.158+0300 WARN failed processing headers {"error": "vm failed to execute the script with error: error encountered at instruction 0 (PUSHDATA1): gas limit is exceeded", "errorVerbose": "vm failed to execute the script with error: error encountered at instruction 0 (PUSHDATA1): gas limit is exceeded\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).verifyHashAgainstScript\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:1454\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).verifyHeaderWitnesses\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:1517\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).verifyHeader\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:1175\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).addHeaders\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:484\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).AddHeaders\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:453\ngithub.com/nspcc-dev/neo-go/pkg/network.(*Server).handleHeadersCmd\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/network/server.go:454\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1373"}
```
Disallow costly verification methods. We put this limit in policy
contract as it may be a subject to change in future.
In fact this value also overrides gas limit for header verification.
Close#1202.
NextBlockValidators are updated before the new block persist, so we need to
use GetValidators to get the list corresponding to the current state of the
chain.
Even if the value is zero, the GAS distribution updates the balance height, so
storage item must be updated too. Fixes the followin on preview2 testnet:
block 74227: value mismatch for key ffffffff1454a6cb279fbcedc66162ad4ad5d1d910202b92743e000000000000000000000005: 1041032104809fd5002103f3210128010000 vs 1041032104809fd50021033f110128010000
They make no sense. Fixes preview2 testnet state problem:
file BlockStorage_100000/dump-block-70000.json: block 69935: state mismatch for key ffffffff1454a6cb279fbcedc66162ad4ad5d1d910202b92743e000000000000000000000005: Deleted vs Added
Preview2 testnet:
file BlockStorage_100000/dump-block-12000.json: block 11562: key mismatch: feffffff1454a6cb279fbcedc66162ad4ad5d1d910202b92743e000000000000000000000005 vs feffffff1431b7e7aea5131f74721e002c6a56b610885813f79e000000000000000000000005
Originally this code was written to run after transactions processing, but
after 0fa4c49735 it works in different manner.
ValidatorsCount is not initialized at block 0 with C# node (the first voter
initializes it) and until that initialization happens the standby validators
list is being returned as is without sorting.
Fixes state mismatch for the key ffffffff0e00000000000000000000000000000001 in
the first blocks.
It also affects tests as now the first validator is different and it receives
the network fees.
MarshalJSON should be defined on structure (not pointer), as we use
structures to marshal parameters (e.g. in NotificationEvent and
Invoke of RPC result package) and never use pointers for that purpose.
Also added marshalling of nil array into `[]` instead of `null` to
follow C# implementation.
