* use ... in BlockInfo protocol
* move prev_block_hash() from BlockchainInterface into BlockRecordsProtocol to transition find_fork_point_in_chain() and lookup_fork_chain() to use the more narrow protocol to lookup the chain
* the WalletBlockchain doesn't need to implement the full BlockchainInterface, but just BlockRecordsProtocol
* remove unused GeneratorBlockCacheInterface and BlockDict
* add unit test for BlockCache
fix lookup_fork_chain() to support starting from an empty chain (i.e. height -1 and header-hash GENESIS_CHALLENGE). There are edge cases where the node may want to do this
* configure isort to add the future annotations import
* apply the new isort setting
* remove type ignores for new mypy (#13539)
https://pypi.org/project/mypy/0.981/
* another