Add a private node to the interactive marker display

[JafarAbdi]

Description

A temporary workaround to fix the lag in the motion planning display interactive marker by adding an internal node & executor

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 #342 (dbd6959) into main (9a86ffb) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #342      +/-   ##
==========================================
+ Coverage   53.23%   53.24%   +0.02%     
==========================================
  Files         209      209              
  Lines       18849    18849              
==========================================
+ Hits        10033    10035       +2     
+ Misses       8816     8814       -2     

Impacted Files	Coverage Δ
...raint_samplers/src/default_constraint_samplers.cpp	77.54% <0.00%> (-0.36%)	⬇️
...nning_scene_monitor/src/planning_scene_monitor.cpp	56.82% <0.00%> (+0.46%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9a86ffb...107ba4b. Read the comment docs.

[henningkayser]

If the fix is really just affecting a native RViz component I'd vote for filing this as an upstream PR. That way this annoying but harmless issue can be avoided by compiling RViz from source and we don't have to maintain additional third-party source files.

[JafarAbdi]

If the fix is really just affecting a native RViz component I'd vote for filing this as an upstream PR.

If a user manually added an interactive marker they will get the native one from RViz, the one here is only used for the interactive marker inside the motion planning display