ros_gz_bridge action requires many of its arguments to be set even though they should be optional

[azeey]

Part of #552

For example, the options container_name, namespace, and use_composition are optional in ros_gz_bridge.launch.py, but require a value when using <ros_gz_bridge> directly. It would be nice if the following worked:

<launch>
  <ros_gz_bridge   config_file='./ros_gz_bridge/test/config/minimum.yaml'  />
</launch>

or

<launch>
  <ros_gz_bridge 
    config_file='./ros_gz_bridge/test/config/minimum.yaml' 
    use_composition='True'/>
</launch>

If #553 is merged, we would have a name parameter in there as well since it will be required.