moved error code enumerations to the result of action messages

[jwallace42]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	None
Primary OS tested on	Ubuntu
Robotic platform tested on	Gazebo

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Description of contribution in a few bullet points

Previously, the error code enumerations were define in the goal section of the action message. This was incorrect because the the error code is a result. This pr moves the error code enumerations for the actions to the result section.

Description of documentation updates required from your changes

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Future work that may be required in bullet points

For Maintainers:

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[mergify]

This pull request is in conflict. Could you fix it @jwallace42?

[SteveMacenski]

I generally approve, seems like a reasonable change!

[codecov]

Codecov Report

Patch coverage: 74.68% and project coverage change: +0.01 🎉

Comparison is base (921eed0) 90.36% compared to head (e6e2181) 90.37%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3693      +/-   ##
==========================================
+ Coverage   90.36%   90.37%   +0.01%     
==========================================
  Files         411      411              
  Lines       17801    17801              
==========================================
+ Hits        16086    16088       +2     
+ Misses       1715     1713       -2     

Impacted Files	Coverage Δ
...ior_tree/plugins/action/assisted_teleop_action.hpp	100.00% <ø> (ø)
...v2_behavior_tree/plugins/action/back_up_action.hpp	100.00% <ø> (ø)
...ugins/action/compute_path_through_poses_action.hpp	100.00% <ø> (ø)
...ree/plugins/action/compute_path_to_pose_action.hpp	100.00% <ø> (ø)
...or_tree/plugins/action/drive_on_heading_action.hpp	100.00% <ø> (ø)
...ehavior_tree/plugins/action/follow_path_action.hpp	100.00% <ø> (ø)
...e/plugins/action/navigate_through_poses_action.hpp	100.00% <ø> (ø)
...or_tree/plugins/action/navigate_to_pose_action.hpp	100.00% <ø> (ø)
...ehavior_tree/plugins/action/smooth_path_action.hpp	100.00% <ø> (ø)
.../nav2_behavior_tree/plugins/action/spin_action.hpp	100.00% <ø> (ø)
... and 24 more

... and 10 files with indirect coverage changes

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[SteveMacenski]

@jwallace42 can you open a PR for migration guide?