Implement abi.encodeWithSelector and abi.encodeWithSignature

[jacky860226]

abi.encodeWithSignature(string memory signature, ...) is equal to abi.encodeWithSelector(bytes4(keccak256(bytes(signature))), ...)
https://docs.soliditylang.org/en/v0.7.1/units-and-global-variables.html?highlight=abi#abi-encoding-and-decoding-functions