Add id and visibility_flags to Projector msg fields

[iche033]

🎉 New feature

Closes #341

Summary

Adding a couple of fields to projector msg

• id: Unique entity id
• visibility_flags: If the projector's visibility flags matches a camera's visibility_mask, then the projector will be visible to the camera.

Related todo note in gz-sim: https://github.com/gazebosim/gz-sim/blob/gz-sim7/src/Conversions.cc#L1790

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• 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 #345 (63c661a) into main (cfe6c2e) will not change coverage.
The diff coverage is n/a.

❗ Current head 63c661a differs from pull request most recent head dfbcef3. Consider uploading reports for the commit dfbcef3 to get more accurate results

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  Hits          983      983           
  Misses         47       47