Create custom ContractType to override selector fn to use starknet_keccak

[antazoey]

Overview

Currently, we cannot access methods the nice way using the keccak selectors with contract types from Cairo.
We should make a custom StarknetContractType in the compiler with its own selector method so the ape-starknet plugin can load method ABIs when its is re-serializing transactions.

Specification

StarknetContractType(ContractType):
  _selector_hash_fn = starknet_keccak

Dependencies

Include links to any open issues that must be resolved before this feature can be implemented.