* PostgreSQL: FIx multiple results handling
- Added tests for handling multiple result sets, including compatible and incompatible structures, ensuring no panics occur.
- Improved `convertResultsToFrame` function to validate column compatibility and handle null values correctly.
- Introduced a new helper function `convertPostgresValue` for converting raw PostgreSQL values to appropriate Go types.
- Added comprehensive unit tests for `convertResultsToFrame` covering various scenarios including row limits and mixed result types.
* Add more test case
