Updated Message Hashing with Cairo's hash_state

[andrew-fleming]

Updated Message Hashing with Cairo's hash_state

Summary

This PR includes the Account contract's custom hash_message and hash_calldata functions refactored to include Cairo's hash_state as referenced in #37 . The hash_message() function first invokes hash_calldata() and saves the reference locally before utilizing hash_state_ptr to iterate through the rest of the message.

Cairo's hash_state.py provides compute_hash_on_elements() to greatly simplify testing. The Signer.py module is updated with this function accordingly.

Implementation

• Removed all hash2() functions from Account.cairo and Signer.py
• Utilized Cairo's hash_state in both hash_message() and hash_calldata()
• Implemented compute_hash_on_elements() appropriately in the Signer.py module

Future

• Perhaps, we can further distill the process and remove hash_calldata() from the Account contract altogether

[martriay]

Very nice.