Preserve metadata when detaching objects

[v4hn]

@corot proposed to fix object color handling, but the handling itself does not seem to be broken the way they expect.

Instead, when trying to remove an attached object from the world, color/type was removed even when the object was not actually removed from the world (attached objects are not in the world, so their meta-data should stay around).

Additionally here is a test to verify handling of color and type works as expected when objects get attached/detached.

@corot The bugfix should help you find the culprit in your use case. Please have a look at the test as well.

[corot]

Yup, much better than my PR, and equally preserves the color
Thanks!

[codecov]

Codecov Report

Merging #2814 (e89a5b6) into master (0defef0) will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2814      +/-   ##
==========================================
+ Coverage   60.42%   60.51%   +0.09%     
==========================================
  Files         366      366              
  Lines       31673    31672       -1     
==========================================
+ Hits        19136    19163      +27     
+ Misses      12537    12509      -28     

Impacted Files	Coverage Δ
moveit_core/planning_scene/src/planning_scene.cpp	60.39% <100.00%> (+1.62%)	⬆️
...meterization/work_space/pose_model_state_space.cpp	83.02% <0.00%> (+1.89%)	⬆️
.../ompl_interface/src/detail/constrained_sampler.cpp	59.46% <0.00%> (+16.22%)	⬆️

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[felixvd]

Right. When we attach the object, we remove it from the world without removing the metadata. This avoids deleting the metadata when detaching the object with the REMOVE keyword.

I still think it would be much easier to understand the code with a DETACH keyword, and/or if the metadata was copied from the AttachedBody to the world, but there are bigger fish to fry.

[felixvd]

LGTM!