Add error_code_to_string function

[sjahr]

Description

Adds convenience function to print a MoveItError code

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Merging #1523 (f8c0a4e) into main (f7655df) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1523      +/-   ##
==========================================
+ Coverage   50.97%   50.98%   +0.01%     
==========================================
  Files         380      380              
  Lines       31758    31758              
==========================================
+ Hits        16187    16188       +1     
+ Misses      15571    15570       -1     

Impacted Files	Coverage Δ
...dl_kinematics_plugin/src/kdl_kinematics_plugin.cpp	75.36% <0.00%> (-1.07%)	⬇️
...nning_scene_monitor/src/planning_scene_monitor.cpp	45.73% <0.00%> (+0.44%)	⬆️

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