Fix data race issues in CameraTracking plugin

[azeey]

🦟 Bug fix

Summary

There are three threads at work here: the main thread, the render thread, and the transport thread. The change is meant to synchronize all of these threads.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• 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

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #537 (2ed3fd8) into ign-gui6 (b3903b0) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 2ed3fd8 differs from pull request most recent head 310fb68. Consider uploading reports for the commit 310fb68 to get more accurate results

@@             Coverage Diff              @@
##           ign-gui6     #537      +/-   ##
============================================
+ Coverage     69.83%   69.85%   +0.01%     
============================================
  Files            40       40              
  Lines          5324     5324              
============================================
+ Hits           3718     3719       +1     
+ Misses         1606     1605       -1     

Impacted Files	Coverage Δ
src/plugins/camera_tracking/CameraTracking.cc	69.04% <100.00%> (+0.59%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.