Compose multiple ROS 2 (Lyrical Luth) nodes into one process using a component container and the ros2 component CLI

Documented steps

1. Ensure rclcpp_components, ros2component, composition and image_tools are installed (standard in a desktop install). List available components: `ros2 component types`.
2. Shell 1 - start a container with the default SingleThreadedExecutor: `ros2 run rclcpp_components component_container`.
3. Shell 2 - verify it is running: `ros2 component list` prints /ComponentManager.
4. Load the talker: `ros2 component load /ComponentManager composition composition::Talker` - returns the component's unique id and node name. Shell 1 begins logging published messages.
5. Load the listener: `ros2 component load /ComponentManager composition composition::Listener`. `ros2 component list` now shows `1 /talker` and `2 /listener`.
6. Unload by id: `ros2 component unload /ComponentManager 1 2`.
7. Pick an executor: `--executor-type multi-threaded --ros-args -p thread_num:=4` for a MultiThreadedExecutor; `--executor-type events-cbg --ros-args -p thread_num:=1` for the EventsCBGExecutor (new in Lyrical, roughly 10-15% lower CPU than the single/multi-threaded executors); `--executor-type multi-threaded --isolated` gives each component its own dedicated executor.
8. Remap the container itself at startup: `ros2 run rclcpp_components component_container --ros-args -r __node:=MyContainer -r __ns:=/ns`, then load against /ns/MyContainer.
9. Remap a loaded component at load time: `ros2 component load /ComponentManager composition composition::Talker --node-name talker3 --node-namespace /ns2`.
10. Pass constructor parameters into a component: `ros2 component load /ComponentManager image_tools image_tools::Cam2Image -p burger_mode:=true`.
11. Pass component-manager options with -e, e.g. `-e use_intra_process_comms:=true -e forward_global_arguments:=false`. Supported keys include forward_global_arguments, enable_rosout, use_intra_process_comms, enable_topic_statistics, start_parameter_services, start_parameter_event_publisher, use_clock_thread and enable_logger_service.
12. To load a whole set at once use a launch file instead of manual CLI calls: `ros2 launch composition composition_demo_launch.py`.
13. Official doc: https://docs.ros.org/en/lyrical/Tutorials/Intermediate/Composition.html