[Spawner] Allow parsing the parameter files parsed from spawner to controllers (backport #3136)

[mergify]

Fixes #3135
Tested with ros-controls/ros2_control_demos#1079

@urfeex FYI

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This is an automatic backport of pull request #3136 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of a583699 has failed:

On branch mergify/bp/kilted/pr-3136
Your branch is up to date with 'origin/kilted'.

You are currently cherry-picking commit a583699.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   controller_manager/test/test_spawner_unspawner.cpp

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   controller_manager/controller_manager/spawner.py
	both modified:   controller_manager/doc/userdoc.rst
	deleted by us:   controller_manager/test/test_advanced_spawner.cpp
	both modified:   doc/release_notes.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

[saikishor]

Will rebase after merging #3053