Fix rendering tests on Jammy

[iche033]

🦟 Bug fix

Summary

Rendering tests have been failing on Jammy github actions for a while. This PR fixes the tests and we should now get a green CI.

It was found that all rendering tests segfault on exit, caused by destructor of rendering objects. The changes in this PR fix the test by cleaning up these pointers. Side note: tests are only failing on Jammy github actions and not on other platforms. I'm also not able to reproduce the failing tests locally. Fixes should also be done on the gz-rendering side to make sure objects can destroyed safely when going out of scope.

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 #324 (ba9a263) into ign-sensors6 (d2dff1a) will not change coverage.
The diff coverage is 100.00%.

❗ Current head ba9a263 differs from pull request most recent head 280b5d6. Consider uploading reports for the commit 280b5d6 to get more accurate results

@@              Coverage Diff              @@
##           ign-sensors6     #324   +/-   ##
=============================================
  Coverage         73.76%   73.76%           
=============================================
  Files                34       34           
  Lines              3510     3510           
=============================================
  Hits               2589     2589           
  Misses              921      921           

Impacted Files	Coverage Δ
src/RenderingSensor.cc	95.00% <100.00%> (ø)

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