rqt_cm: Fix handling of unconfigured controllers during spawn action (backport #1794)

[mergify]

Description:

This PR addresses an #1791 issue where controllers in the "unconfigured" state were being loaded rather than configured during the action_spawn process. The previous behavior could lead to errors when attempting to activate controllers that were not yet configured.

Changes made:

• Updated the handling of the "unconfigured" state to configure the controller when the action is action_spawn, ensuring proper configuration before activation.
• This replaces the previous use of load_controller during action_spawn.

Testing:

I was unable to test the changes with diffbot.launch.py due to build issues with ros2_controllers on my system running ROS Iron, as the rolling build is not compatible with iron.

---

This is an automatic backport of pull request #1794 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.32%. Comparing base (3aa31c5) to head (849220d).
Report is 1 commits behind head on humble.

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1797      +/-   ##
==========================================
- Coverage   62.34%   62.32%   -0.02%     
==========================================
  Files         108      108              
  Lines       11412    11412              
  Branches     7979     7982       +3     
==========================================
- Hits         7115     7113       -2     
- Misses        820      822       +2     
  Partials     3477     3477              

Flag	Coverage Δ
unittests	62.32% <ø> (-0.02%)	⬇️

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see 1 file with indirect coverage changes