[neox] Merge neox to master

[ZhangTao1596]

MPT Integration Specification

introduction

As we have already merged MPT into neo, now it's time for us to integrate it with neo. In this article, I will clarify the detail of the solution in neox.

persistence

Using DataCache implemented by MPT, we can replace the Storage in snapshot as the contracts' storage.

SnapshotView

Field	Type	Description
Blocks	StoreDataCache<UInt256, TrimmedBlock>
Transactions	StoreDataCache<UInt256, TransactionState>
Contracts	StoreDataCache<UInt160, ContractState>
HeaderHashList	StoreDataCache<SerializableWrapper, HeaderHashList>
BlockHashIndex	StoreMetaDataCache
HeaderHashIndex	StoreMetaDataCache
ContractId	StoreMetaDataCache
LocalStateRoot	StoreDataCache<SerializableWrapper, HashIndexState>	State root hash of every block calculated by local node
ValidatorsStateRoot	StoreMetaDataCache	State root verified by validators, only store the latest one
Storages	MPTDataCache<StorageKey, StorageItem>	Storage of contracts, implemented with MPT

consensus

Validators confirm state root of a block in next consensus.
Primary node proposal PrepareRequest with signature of previous block state root. Backup nodes verify the state root signature with their local state root and send their signatures in PrepareResponse if succeed.
As long as a validator collects M preparation messages, it can generate state root of last block.
Because state root is a determined value, validators just vote for right or not. Therefore validators can determine state root in one consensus turn.

PrepareRequest

Field	Type	Description
Timestamp	ulong
Nonce	ulong
TransactionHashes	UInt256[]
StateRootSignature	byte[]	signature of previous block state root

PrepareResponse

Field	Type	Description
PreparationHash	UInt256
StateRootSignature	byte[]	signature of previous block state root

network

State root defination and GetStateRoot message for state root sync.

StateRoot

Field	Type	Description
Version	byte	Version of state root caculate algorithm
Index	uint	Index of block which state root is calculated from
RootHash	UInt256	State root hash
Witness	Witness	Verification script and invocation script

GetStateRoot

Field	Type	Description
Index	uint	The minimum index of the requested stateroot

ledger

​ When receiving the block, the node will calculate state root after the persist is completed, and it will check the state root cache for state root of the block that have been confirmed by the validators.
​ When receiving state root signed by validators, the node will check and verify it and compare it with local state root, update state height if they are equal.

[roman-khimov]

It's a bit disappointing to see #1526 being completely ignored. With all respect to the work done for neox, this design is fine for Neo 2, but we should do better for Neo 3. And it's not the code that's problematic, the code is fine, the problem is in the design of this feature and we either roll over all the problems of it from Neo 2 to Neo 3 or we make something better right from the genesis. I've thought that Neo 3 usually does the second.

[vncoelho]

Beautiful!
Congratulations to all the team for working hard on it,following historical discussions precisely.

After merging master I will take another review, in particular, on consensus.

[ZhangTao1596]

Move to #1793, because conficts and error.