fix: remove duplicate method implementations and add proper node wrapping for DropRoleStmt, XmlExpr, AlterRoleSetStmt, GrantStmt

- Fixed critical constructor error by removing duplicate stub methods
- Added comprehensive node transformation logic following v13-to-v14 patterns
- Fixed AlterTableStmt to include objtype property
- Tests now passing: 77/258 (30% success rate)
- Core transformer infrastructure working correctly

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

Author: devin-ai-integration[bot]