Add ESC to unselect entities in select entities plugin

[ahcorde]

🦟 Bug fix

Summary

ESC to unselect entities

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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[codecov]

Codecov Report

Merging #995 (74715e1) into main (1334b5c) will decrease coverage by 0.00%.
The diff coverage is n/a.

❗ Current head 74715e1 differs from pull request most recent head 438ebba. Consider uploading reports for the commit 438ebba to get more accurate results

@@            Coverage Diff             @@
##             main     #995      +/-   ##
==========================================
- Coverage   63.79%   63.78%   -0.01%     
==========================================
  Files         246      246              
  Lines       19996    19996              
==========================================
- Hits        12756    12755       -1     
- Misses       7240     7241       +1     

Impacted Files	Coverage Δ
src/gui/plugins/plot_3d/Plot3D.cc	43.47% <0.00%> (-4.35%)	⬇️
src/SimulationRunner.cc	93.90% <0.00%> (+1.01%)	⬆️

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[ahcorde]

@osrf-jenkins retest this please