Use gz-cmake

[chapulina]

🎉 New feature

Requires

• https://github.com/osrf/homebrew-simulation/pull/1944
• https://github.com/gazebo-tooling/release-tools/pull/749
• https://github.com/gazebo-tooling/gazebodistro/pull/113

Summary

Reduce duplication with other Gazebo libraries by depending on gz-cmake.

There's been a previous attempt at migrating to gz-cmake in PR 6, but at the time we decided against it because it would be complicated to support two versions installing the ign executable. With the move to gz (see https://github.com/gazebo-tooling/release-tools/issues/739), that's no longer an issue.

Test it

• Build this package with colcon
• Build some package that depends on it, like gz-plugin, and check that the gz plugin CLI works
• Run colcon test and check that UNIT_gz_TEST and rubocop passed
• Run colcon build --cmake-target doc, then navigate to build/ignition-tools2/doxygen/html/ and check that the documentation site is correctly generated
• Run colcon build --cmake-target codecheck and check it passes

Checklist

• [x] Signed all commits for DCO
• [x] Added tests
• [x] Added example and/or tutorial
• [x] Updated documentation (as needed)
• [x] Updated migration guide (as needed)
• [x] Consider updating Python bindings (if the library has them)
• [x] codecheck passed (See contributing)
• [x] All tests passed (See test coverage)
• [x] 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.

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