Add debugging informative log statement for a common error

[PeterMitrano]

Description

If the user calls setJointValueTarget with the wrong number of joint values, it just returns false without providing any information as to what went wrong. Personally when something in moveit goes wrong the first thing I do is turn on debug logging so this would help in that case.

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

[simonschmeisser]

👍

not sure if you want to include the group name as well?

[codecov]

Codecov Report

Merging #2509 (1eadf26) into master (4788419) will increase coverage by 3.57%.
The diff coverage is 97.82%.

@@            Coverage Diff             @@
##           master    #2509      +/-   ##
==========================================
+ Coverage   56.68%   60.24%   +3.57%     
==========================================
  Files         281      351      +70     
  Lines       25455    26475    +1020     
==========================================
+ Hits        14426    15948    +1522     
+ Misses      11029    10527     -502     

Impacted Files	Coverage Δ
...lude/moveit/collision_detection/collision_common.h	93.94% <ø> (+13.94%)	⬆️
...sion_detection_bullet/src/collision_env_bullet.cpp	78.38% <0.00%> (-0.44%)	⬇️
.../moveit/collision_detection_fcl/collision_common.h	100.00% <ø> (+11.30%)	⬆️
.../collision_detection_fcl/src/collision_env_fcl.cpp	88.42% <0.00%> (-0.23%)	⬇️
...on_distance_field/collision_distance_field_types.h	49.16% <ø> (-0.84%)	⬇️
...del/include/moveit/robot_model/joint_model_group.h	100.00% <ø> (ø)
moveit_core/robot_state/src/robot_state.cpp	50.00% <0.00%> (+3.87%)	⬆️
...rial_motion_planner/src/velocity_profile_atrap.cpp	100.00% <ø> (ø)
...pilz_industrial_motion_planner_testutils/basecmd.h	100.00% <ø> (ø)
..._motion_planner_testutils/cartesianconfiguration.h	44.45% <ø> (ø)
... and 372 more

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[PeterMitrano]

sure, why not. I've added dded the group name. Thanks for the speedy approve!