Implement GasGuard optimization rules and Yul performance utilities

[suleimanjem-hash]

Summary

This PR introduces new GasGuard optimization rules alongside gas-efficient Yul utility implementations aimed at improving smart contract performance and developer guidance.

Changes

• Implemented G012 to detect expensive dynamic string equality comparisons and recommend using fixed bytes32 constants or hash identifiers.
• Implemented G013 to detect redundant self-directed external calls (this.function()) and recommend replacing them with internal function calls.
• Added a gas-optimized Yul byte array concatenation utility that minimizes memory allocations by writing directly to contiguous free memory.
• Added a gas-optimized Yul EIP-712 typed data hashing utility with optimized domain separator and typed data digest computation using inline assembly.
• Added Solidity fixture files and comprehensive unit tests covering expected behavior and edge cases for the new rules and utilities.

Benefits

• Reduces unnecessary gas consumption in common Solidity patterns.
• Improves developer feedback through additional static analysis rules.
• Introduces reusable low-level Yul utilities for memory-efficient operations.
• Maintains compatibility with existing functionality while extending GasGuard's optimization capabilities.

Closes

• Closes [RULE] Rule G012: Flag Direct String Equality Operators #682
• Closes [RULE] Rule G013: Detect Internal Redundant External Call Invocations #685
• Closes [PERF] Implement Gas-Efficient Byte Array Concatenator in Yul #686
• Closes [PERF] Build Gas-Optimized EIP-712 Typed Data Hash Calculator #688

[drips-wave]

@suleimanjem-hash Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits