Enhance EIP-1271 signature support in SafeTestTools

[arawrdn]

Summary

This PR enhances the EIP-1271 signature verification capabilities in SafeTestTools, allowing more flexible and robust testing of contract signatures.

Changes

1. Added EIP1271Utils.sol helper library to verify signatures from any contract implementing EIP-1271.
2. Supported multiple signature formats (eth_sign, personal_sign, and EIP712) for testing purposes.
3. Added eip1271.test.js to validate signature verification logic with mock contracts.
4. Provided example usage in scripts/testEIP1271.js to demonstrate integration in tests.

Why

Currently, SafeTestTools only supports basic EIP-1271 verification. These changes enable developers to:

• Verify signatures from any contract implementing EIP-1271.
• Test multiple signature formats.
• Simplify writing tests involving Safe contracts with different signers.

Test Plan

• Run npx hardhat test to ensure all new tests pass.
• Verify example script executes without errors on local fork.

[colinnielsen]

hey thanks for contributing. this project does not use hardhat on purpose - can you please update your tests to use foundry?