Improve parameter handling (backport #664)

[mergify]

🦟 Bug fix

Summary

Builds on top of #663 and improves parameter handling so that <param> tags can be used in XML just like how it's used in <node> tags. Previously, the the bridge_params parameter was used and there was some custom parsing in the code. This PR uses code from launch_ros/actions/node.py so we get all the parsing for free.

So to set qos overrides, it would look like

<ros_gz_bridge 
    bridge_name="ros_gz_bridge"
    config_file="$(find-pkg-share ros_gz_sim_demos)/config/air_pressure.yaml"
    use_composition="false">
    
  <param name="qos_overrides./air_pressure.subscription.reliability" value="best_effort" />
</ros_gz_bridge>

Instead of

  <ros_gz_bridge
    bridge_name="ros_gz_bridge"
    config_file="$(find-pkg-share ros_gz_sim_demos)/config/air_pressure.yaml"
    use_composition="true"
    bridge_params="'qos_overrides./air_pressure.publisher.reliability': 'best_effort'" />

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• 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 and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

---

This is an automatic backport of pull request #664 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 705ee56 has failed:

On branch mergify/bp/jazzy/pr-664
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Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both added:      .github/workflows/ros2-ci.yml
	both added:      README.md
	both added:      ros_gz/CHANGELOG.rst
	both added:      ros_gz/package.xml
	both added:      ros_gz_bridge/CHANGELOG.rst
	both added:      ros_gz_bridge/package.xml
	both added:      ros_gz_image/CHANGELOG.rst
	both added:      ros_gz_image/package.xml
	both added:      ros_gz_interfaces/CHANGELOG.rst
	both added:      ros_gz_interfaces/package.xml
	both added:      ros_gz_sim/CHANGELOG.rst
	both added:      ros_gz_sim/package.xml
	both added:      ros_gz_sim_demos/CHANGELOG.rst
	both added:      ros_gz_sim_demos/package.xml
	both added:      test_ros_gz_bridge/CHANGELOG.rst
	both added:      test_ros_gz_bridge/package.xml

no changes added to commit (use "git add" and/or "git commit -a")

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