In setuptools packages, install everything in launch directory (backport #5156)

[mergify]

Part of #5143

Instead of using "clever" glob pattern to match launch.xml, launch.yaml, launch.py - just copy what we already recommend for CMake packages, and install everything from launch/ directory. Benefit of consistency between package types, and potentially leaving the door open for other launch suffixes/frontends.

(also, make our usage of glob consistent across the repo - we were some places using os.path.join inside it, and sometimes not. I opted for the simpler syntax)

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This is an automatic backport of pull request #5156 done by Mergify.

[mergify]

Cherry-pick of d002d60 has failed:

On branch mergify/bp/humble/pr-5156
Your branch is up to date with 'origin/humble'.

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  (fix conflicts and run "git cherry-pick --continue")
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Changes to be committed:
	modified:   source/Tutorials/Beginner-Client-Libraries/Using-Parameters-In-A-Class-Python.rst
	modified:   source/Tutorials/Intermediate/Launch/Launch-system.rst
	modified:   source/Tutorials/Intermediate/Launch/Using-Substitutions.rst
	modified:   source/Tutorials/Intermediate/Tf2/Writing-A-Tf2-Broadcaster-Py.rst
	modified:   source/Tutorials/Intermediate/URDF/Using-URDF-with-Robot-State-Publisher-py.rst

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   source/How-To-Guides/Developing-a-ROS-2-Package.rst
	both modified:   source/Tutorials/Intermediate/Launch/Using-ROS2-Launch-For-Large-Projects.rst

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

HTML artifacts: https://github.com/ros2/ros2_documentation/actions/runs/14065047042/artifacts/2817362914.

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