Simplify scene update that does not include new robot_state

[MarqRazz]

Description

Updates changes applied in #3187 to match the back port to MoveIt1.

[rhaschke]

I assume you verified that this simplification still fixes your original issue.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.64%. Comparing base (80c7f61) to head (1892706).
Report is 1 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3206      +/-   ##
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- Coverage   45.64%   45.64%   -0.00%     
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  Files         714      714              
  Lines       62286    62284       -2     
  Branches     7530     7529       -1     
==========================================
- Hits        28426    28424       -2     
+ Misses      33694    33693       -1     
- Partials      166      167       +1     

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[MarqRazz]

Yes I verified that this does fix my issue. FYI I do see small differences between the diff scene_ and CSM, for example
[move_group.moveit.moveit.ros.planning_scene_monitor ]: CSM: 0.814504, diff scene_: 0.812823, but it is so small it is not effecting my motion plans like it was before.

[rhaschke]

I do see small differences between the diff scene_ and CSM, for example CSM: 0.814504, diff scene_: 0.812823

I guess those are some randomly picked joint values?
CSM updates are much more frequent than PS updates. If the robot gets to rest, they should become identical eventually.

[rhaschke]

Let's wait for moveit/moveit#3683 before merging this.

[MarqRazz]

I guess those are some randomly picked joint values? CSM updates are much more frequent than PS updates. If the robot gets to rest, they should become identical eventually.

That is showing values for joint_1 of my robot when newPlanningSceneMessage is called with scene.is_diff=false and an empty joint_state. At this point of my setup the robot motion is complete so it depends on the last time the planning_scene_monitor updated it's robot_state / published at it's 2Hz rate if will include this small change in position.

[sea-bass]

I think your commit invalidated the other approving reviews. Here's another!