Marker: support different colors per point

[chapulina]

🎉 New feature

• Part of Generic point cloud visualization gz-sim#1156
• Requires Bump in Garden: ign-msgs and dependents gazebo-tooling/release-tools#554

Summary

The goal is to be able to display points with different colors. Right now, that's possible using one point per Marker message inside a Marker_V, but that hurts performance because there's a lot of duplication on each nested message.

The approach taken here is similar to the marker message on RViz.

Points only really need one color, they currently only use diffuse from the material field. I decided to go with a full Material message instead of just a plain color because we may want to use this field for other things like triangles in the future.

The branch is currently on ign-msgs8 while I work on the implementation, but the goal is to merge this into main after gazebo-tooling/release-tools#554. Rebased onto main.

Test it

There's a demo on ign-gui:

• Set per-point color on markers gz-gui#318

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• 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 #202 (255ed82) into main (3074522) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #202   +/-   ##
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  Coverage   84.56%   84.56%           
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  Files           7        7           
  Lines         855      855           
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  Hits          723      723           
  Misses        132      132           

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[caguero]

Works for me!