feat: ci storage check required

[0xClandestine]

Motivation:

Storage layout checker was incorrectly treating __gap variable overrides as critical errors, despite this being their intended use in upgradeable contracts.

Modifications:

• Added special handling for __gap variables
• Split issues into critical errors (storage overrides, removals) and warnings (gap overrides, renames)
• Updated error messages and return values accordingly

Result:

Script now properly validates storage layout changes, only failing on actually dangerous modifications while allowing intended gap usage.