Managing hooks

For similar reasons as the asset registry, the Aera client is responsible for managing the hooks contract.

This currently entails maintaining the target sighash allowlist which governs the type of contracts and operations on those contracts that the gurdian can submit for execution

It's critical that the client independently evaluates the correctness of any calldata sent to the hooks contract. Adding an target sighash pair is a sensitive operation that could needlessly empower the guardian.