PBHSignatureAggregator

[karankurbur]

• change interface to remove view modifier from validateSignatures and validateUserOpSignature. This is required since we may have state change inside PBHValidator
• create PBHSignatureAggregator that inherit the BLSSignatureAggregator class
• add new function to return encoded BLS signature + proofs array
• modify the validateSignatures and validateUserOpSignature to remove the proof before verifying the BLS signature through the BLSSignatureAggregator
• verify the proof through PBHVerifier

TODO:

• Check E2E if modifying the interface reverts from EntryPoint
• Unit tests to validate encoding/decoding logic
• Refactor BLSSignatureAggregator to use created internal functions