Refactor and update ROS 2 point cloud processing nodes

- Updated submodule reference for Universal_Robots_ROS2_Gazebo_Simulation.
- Removed `moveit_stop.py` and `random_pcl.py` files as they are no longer needed.
- Renamed and refactored `serial_to_pcl_node.py` to `moveit_stop_node.py` with enhanced functionality for trajectory execution based on point cloud data.
- Updated `serial_to_pcl_node.py` to include distance filtering for published point clouds.
- Deleted `test_transform.py` as it is redundant with the new implementations.
- Updated `setup.py` to reflect changes in node names and structure.
- Added new implementations for `pcl_filter_node.py` and `random_pcl_pub_node.py` to improve point cloud generation and filtering capabilities.
- Enhanced point cloud processing logic to improve performance and maintainability.