Add option to change material color from ROS. (backport #521)

[mergify[bot]]

Forward port of PR #486 from humble to iron

* Message and bridge for MaterialColor.

This allows bridging MaterialColor from ROS to GZ and is
important for allowing simulation users to create status lights.

➡️ Forward port

Single feature forward port from modified cherry-pick

Note to maintainers: Remember to Merge with commit (not squash-merge or rebase)

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This is an automatic backport of pull request #521 done by Mergify.