Improve performance of ECM::Entit(y|ies)ByComponents and ECM::ChildrenByComponents (backport #3375)

[mergify]

🦟 Bug fix

Summary

This is a follow up optimization from Follow up from #3362 where components are retrieved from the view instead of via ECM::Component<T>, which is expensive. Since the view caches the components, access to these components has the same performance characteristics as ECM::Each.

Checklist

• Signed all commits for DCO
• Added a screen capture or video to the PR description that demonstrates the fix (as needed)
• 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)
• Updated Bazel files (if adding new files). Created an issue otherwise.
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• Was GenAI used to generate this PR? If so, make sure to add "Generated-by" to your commits. (See this policy for more info.)

Generated-By: Gemini 3.0

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This is an automatic backport of pull request #3375 done by Mergify.

[mergify]

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	both modified:   include/gz/sim/detail/EntityComponentManager.hh

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