slither-read-storage native POA support

[webthethird]

Adds a new RpcInfo class that holds self.rpc, self.web3 and self.block, which are removed from SlitherReadStorage. SlitherReadStorage gets new self._rpc_info: Optional[RpcInfo] which is required for using Web3.

In RpcInfo, automatically detect if the network is POA when setting self._block. web3.eth.get_block raises an ExtraDataLengthError when using an RPC for a POA network, so if we catch one of those after trying to set self._block, we know it is a POA network and therefore inject the appropriate middleware.

[webthethird]

I'm running into an error in web3.eth.get_block when passing in an enum element, even though its value is a string.

    def test_read_storage(web3, ganache) -> None:
        assert web3.is_connected()
        bin_path = Path(TEST_DATA_DIR, "StorageLayout.bin").as_posix()
        abi_path = Path(TEST_DATA_DIR, "StorageLayout.abi").as_posix()
        bytecode = get_source_file(bin_path)
        abi = get_source_file(abi_path)
        contract = deploy_contract(web3, ganache, bytecode, abi)
        contract.functions.store().transact({"from": ganache.eth_address})
        address = contract.address
    
        sl = Slither(Path(TEST_DATA_DIR, "storage_layout-0.8.10.sol").as_posix())
        contracts = sl.contracts
    
>       rpc_info: RpcInfo = RpcInfo(ganache.provider, BlockTag.LATEST)

test_read_storage.py:106: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../../slither/tools/read_storage/read_storage.py:73: in __init__
    self._block: int = self.web3.eth.get_block(block)["number"]
../../../../../.local/lib/python3.10/site-packages/web3/eth/eth.py:389: in get_block
    return self._get_block(block_identifier, full_transactions)
../../../../../.local/lib/python3.10/site-packages/web3/module.py:58: in caller
    (method_str, params), response_formatters = method.process_params(
../../../../../.local/lib/python3.10/site-packages/web3/method.py:214: in process_params
    self.json_rpc_method = self.method_choice_depends_on_args(value=params[0])
cytoolz/functoolz.pyx:253: in cytoolz.functoolz.curry.__call__
    ???
cytoolz/functoolz.pyx:249: in cytoolz.functoolz.curry.__call__
    ???
../../../../../.local/lib/python3.10/site-packages/web3/_utils/blocks.py:62: in select_method_for_block_identifier
    if is_predefined_block_number(value):
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

value = <BlockTag.LATEST: 'latest'>

    def is_predefined_block_number(value: Any) -> bool:
        if is_text(value):
            value_text = value
        elif is_bytes(value):
            # `value` could either be random bytes or the utf-8 encoding of
            # one of the words in: {"latest", "pending", "earliest", "safe", "finalized"}
            # We cannot decode the bytes as utf8, because random bytes likely won't be
            # valid. So we speculatively decode as 'latin-1', which cannot fail.
            value_text = value.decode("latin-1")
        elif is_integer(value):
            return False
        else:
>           raise TypeError(f"unrecognized block reference: {value!r}")
E           TypeError: unrecognized block reference: <BlockTag.LATEST: 'latest'>

I'm thinking it might be better to use the pre-existing web3.types.BlockParams instead of the new BlockTag enum:
BlockParams = Literal["latest", "earliest", "pending", "safe", "finalized"]

[webthethird]

test_read_storage is passing on my machine, but for some reason the assert web3.is_connected() is failing here

=========================== short test summary info ===========================
FAILED tests/tools/read-storage/test_read_storage.py::test_read_storage - assert False
 +  where False = <bound method Web3.is_connected of <web3.main.Web3 object at 0x0000020F37819AF0>>()
 +    where <bound method Web3.is_connected of <web3.main.Web3 object at 0x0000020F37819AF0>> = <web3.main.Web3 object at 0x0000020F37819AF0>.is_connected

[webthethird]

The more I look at it, the more it seems like introducing the BlockTag enum just over-complicates the code.
Looking at web3._utils, this is similar to what we were doing before introducing that enum:

def parse_block_identifier(
    w3: "Web3", block_identifier: BlockIdentifier
) -> BlockIdentifier:
    if block_identifier is None:
        return w3.eth.default_block
    if isinstance(block_identifier, int):
        return parse_block_identifier_int(w3, block_identifier)
    elif block_identifier in ["latest", "earliest", "pending", "safe", "finalized"]:
        return block_identifier
    elif isinstance(block_identifier, bytes) or is_hex_encoded_block_hash(
        block_identifier
    ):
        return w3.eth.get_block(block_identifier)["number"]
    else:
        raise BlockNumberOutofRange

I am leaning toward going back to this and removing BlockTag:

class RpcInfo:
    def __init__(self, rpc_url: str, block: BlockIdentifier = "latest") -> None:
        assert isinstance(block, int) or block in ["latest", "earliest", "pending", "safe", "finalized"]
        ...

[webthethird]

I am leaning toward going back to this and removing BlockTag

@0xalpharush I went ahead and changed it back

[0xalpharush]

I think we can squash and merge this