Add EntitySemantics system that enables setting categories and tags (backport #3005)

[mergify]

🎉 New feature

Summary

System for assigning semantics to entities, such as models, by classifying them into categories and assigning them tags.

Reference:
https://github.com/ros-simulation/simulation_interfaces/blob/1.0.0/msg/EntityCategory.msg,
https://github.com/ros-simulation/simulation_interfaces/blob/1.0.0/msg/TagsFilter.msg

This system is meant to be attached to a <world>, but it parses parameters
found in entities such as models.

Example:

<model name="robot1">
  <gz:semantics>
    <category>ROBOT</category>
    <tag>mobile</tag>
    <tag>diff_drive</tag>
  </gz:semantics>
</model>

This is a nice to have for gazebosim/ros_gz#790 in order to implement the GetEntityInfo service as well as to allow filtering based on categories and tags in GetEntities

Test it

bin/INTEGRATION_entity_semantics_system 

Future work:

• Service to set categories dynamically. This would be used to implement SetEntityInfo
• Potentially consolidate this and the Label system which is used to add semantic labels to visuals for segmentation.

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
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---

This is an automatic backport of pull request #3005 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of a503633 has failed:

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  (fix conflicts and run "git cherry-pick --continue")
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Changes to be committed:
	new file:   include/gz/sim/components/SemanticCategory.hh
	new file:   include/gz/sim/components/SemanticDescription.hh
	new file:   include/gz/sim/components/SemanticTags.hh
	modified:   src/systems/CMakeLists.txt
	new file:   src/systems/entity_semantics/CMakeLists.txt
	new file:   src/systems/entity_semantics/EntitySemantics.cc
	new file:   src/systems/entity_semantics/EntitySemantics.hh
	modified:   test/integration/CMakeLists.txt
	new file:   test/integration/entity_semantics_system.cc
	new file:   test/worlds/entity_semantics.sdf

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   BUILD.bazel

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[azeey]

Can I get a review since I fixed conflicts?

[iche033]

looks good to me