BlockchainInterface as a protocol

[arvidn]

This PR is best reviewed one commit at a time.

Purpose:

Prepare for adding a new implementation of BlockchainInterface by:

• turn BlockchainInterface into a Protocol and fix-up BlockCache and WalletBlockchain. This enables mypy to check these classes and fail if they don't implement the protocol.
• Split out a small subset of BlockchainInterface into its own protocol, BlockRecordsProtocol. BlockchainInterface subsumes it. Most functions that take a BlockchainInterface today really only need the, simpler, BlockRecordsProtocol. So transition some function calls to take it instead.
• Break out a class BlockchainMock (essentially the same as BlockCache) that implements BlockchainInterface and simplify BlockCache to only implement BlockRecordsProtocol. This moves a large amount of code out from production to testing utilities. The main use case of the BlockchainInterface is in tests where we mock the blockchain class.

Current Behavior:

• BlockchainInterface is of questionable value and does not help type checking.
• Most functions that take the BlockchainInterface don't need most of its complexity.
• most of the functionality of BlockCache is for the benefit of a few tests.

New Behavior:

• BlockchainInterface is a python protocol, which subsumes (a simpler) BlockRecordsProtocol which most of production code uses.
• BlockCache is simple and only supports what the production code requires (implementing BlockRecordInterface).
• A new test class (BlockchainMock) implements the test functionality that previously was covered by BlockCache

Testing Notes:

[coveralls-official]

Pull Request Test Coverage Report for Build 10468518822

Details

• 165 of 189 (87.3%) changed or added relevant lines in 19 files are covered.
• 33 unchanged lines in 10 files lost coverage.
• Overall coverage decreased (-0.003%) to 90.826%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
chia/_tests/util/blockchain_mock.py	69	80	86.25%
chia/wallet/wallet_blockchain.py	17	30	56.67%

Files with Coverage Reduction	New Missed Lines	%
chia/full_node/full_node.py	1	86.06%
chia/daemon/server.py	1	83.25%
chia/wallet/util/wallet_sync_utils.py	2	86.06%
chia/full_node/weight_proof.py	2	90.35%
chia/server/node_discovery.py	2	78.9%
chia/server/server.py	2	82.21%
chia/server/ws_connection.py	2	88.69%
chia/rpc/rpc_server.py	3	87.83%
chia/wallet/wallet_node.py	7	88.22%
chia/timelord/timelord.py	11	80.49%

Totals
Change from base Build 10461877247:	-0.003%
Covered Lines:	101359
Relevant Lines:	111569

---

💛 - Coveralls

[arvidn]

I'm not sure what to do about the test coverage.

1. the BlockchainMock class (formerly BlockCache) has never had unit tests. Now it's also a pure test utility itself.
2. The WalletBlockchain probably doesn't need to implement everything in BlockchainInterface, but the work to tease that a part to remove some of these unused functions is a bit of a rabbit hole (and a distraction from the goal I'm working towards)

[github-actions]

File	Coverage	Missing Lines
chia/_tests/util/blockchain_mock.py	86.2%	lines 43, 46, 73, 79, 97-100, 103, 106, 128
chia/wallet/wallet_blockchain.py	56.7%	lines 216, 222, 225, 228, 231, 236, 239, 242, 248, 251-253, 258

Total	Missing	Coverage
189 lines	24 lines	87%

[wjblanke]

aok