feat: systematic PG14->PG15 transformer improvements

- Updated 50+ transformation methods to use proper transformGenericNode and wrapping
- Improved test coverage from 6/258 to 145/258 tests passing (56% improvement)
- Fixed node wrapping issues for most statement types following v13-to-v14 patterns
- Core transformation logic working for object-to-array conversion and basic transformations
- Remaining issues: boolean TypeCast transformations and A_Const structure handling

Progress: 145/258 tests now passing, representing major improvement in transformer functionality

Co-Authored-By: Dan Lynch <[email protected]>

Author: devin-ai-integration[bot]