Support type description service

[minggangw]

Related rclpy implementation: https://github.com/ros2/rclpy/blob/a7c8631c7af567b01adc15406bd02825b5276642/rclpy/src/rclpy/type_description_service.cpp#L26

Related rcl functions to be leveraged:

• rcl_node_type_description_service_init
• rcl_node_type_description_service_handle_request

Related msg and srv: https://github.com/ros2/rcl_interfaces/tree/rolling/type_description_interfaces