Enable QoS overrides

[chapulina]

🎉 New feature

Summary

From Galactic, it's possible to enable QoS overrides for nodes. This is very important for ros_ign_bridge because different topics may require different QoS settings. For example, sensor data should may be published as best-effort, and commands should be subscribed to as reliable.

This demo is a helpful example.

Test it

The air pressure demo has been updated to override the default reliability (reliable) with best-effort:

1. ros2 launch ros_ign_gazebo_demos air_pressure.launch.py
2. ros2 topic info /air_pressure --verbose

Type: sensor_msgs/msg/FluidPressure                                                                                                         
                                                                                                                                            
Publisher count: 1                                                                                                                          
                                                                                                                                            
Node name: ros_ign_bridge                                                                                                                   
Node namespace: /                                                                                                                           
Topic type: sensor_msgs/msg/FluidPressure                                                                                                   
Endpoint type: PUBLISHER                                                                                                                    
GID: 78.7d.10.01.cc.4b.05.8d.7e.a3.c3.e2.00.00.16.03.00.00.00.00.00.00.00.00                                                                
QoS profile:                                                                                                                                
  Reliability: BEST_EFFORT                                                                                                                  
  Durability: VOLATILE                                                                                                                      
  Lifespan: 2147483651294967295 nanoseconds                                                                                                 
  Deadline: 2147483651294967295 nanoseconds                                                                                                   Liveliness: AUTOMATIC                                                                                                                     
  Liveliness lease duration: 2147483651294967295 nanoseconds                                                                                                                                                                                       
...

Checklist

• Signed all commits for DCO
• Added tests (thought of it, but it would really be adding lots of new lines to test rclcpp)
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge

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[chapulina]

Thanks for the recommendations, @jacobperron . It would be great if you could do a quick review. Thanks!

[jacobperron]

Sorry for the delay. LGTM!