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 62.20%. Comparing base (1fbe5e6) to head (d6bca53).
Report is 1 commits behind head on iron.

Additional details and impacted files

@@            Coverage Diff             @@
##             iron    #1798      +/-   ##
==========================================
+ Coverage   62.18%   62.20%   +0.01%     
==========================================
  Files         112      112              
  Lines       12303    12303              
  Branches     8602     8602              
==========================================
+ Hits         7651     7653       +2     
  Misses        883      883              
+ Partials     3769     3767       -2     

Flag	Coverage Δ
unittests	62.20% <ø> (+0.01%)	⬆️

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see 2 files with indirect coverage changes