Remove the unused bytes parameter from the checkSignatures methods

[mmv08]

When working on the account specifications for the Safe{Core} Protocol, one of the requirements for the signature validators was the checkSignatures(bytes32, bytes, bytes) function, where the second bytes param is unused and comes from the legacy roots in the Safe.

Nick proposed that we remove this param from the requirements to not add "Tech debt" to accounts and update the Safe implementation accordingly.

Proposed solution

• Update the functions in the safe core contract
• Add old methods to the CompatibilityFallbackHandler