[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

---

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/jazzy/pr-3136
Your branch is up to date with 'origin/jazzy'.

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 #3052

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.24%. Comparing base (6449808) to head (69a2dbb).
⚠️ Report is 1 commits behind head on jazzy.

Files with missing lines	Patch %	Lines
controller_manager/controller_manager/spawner.py	80.00%	2 Missing and 3 partials ⚠️
controller_manager/test/test_advanced_spawner.cpp	91.66%	0 Missing and 1 partial ⚠️
controller_manager/test/test_spawner_unspawner.cpp	91.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            jazzy    #3151      +/-   ##
==========================================
+ Coverage   89.21%   89.24%   +0.02%     
==========================================
  Files         158      158              
  Lines       19349    19397      +48     
  Branches     1567     1577      +10     
==========================================
+ Hits        17262    17310      +48     
+ Misses       1450     1447       -3     
- Partials      637      640       +3     

Flag	Coverage Δ
unittests	89.24% <85.71%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
controller_manager/test/test_advanced_spawner.cpp	94.68% <91.66%> (-0.14%)	⬇️
controller_manager/test/test_spawner_unspawner.cpp	96.16% <91.66%> (-0.13%)	⬇️
controller_manager/controller_manager/spawner.py	75.36% <80.00%> (+1.27%)	⬆️

... and 2 files with indirect coverage changes

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