Support building with gz-cmake3 or gz-cmake4

[azeey]

🎉 New feature

Part of gazebo-tooling/release-tools#1027

Summary

We are bumping gz-cmake for Ionic to version 4, which would normally mean we would bump gz-tools, but this would prevent us from being able to install Ionic side-by-side with Harmonic and any older Gazebo collection. To remedy that, since we are not relying on any shared libraries from gz-cmake, we can support building with either gz-cmake3 or gz-cmake4.

Test it

• test with gz-cmake3 by installing it and trying to build this PR
• test with gz-cmake4 by building the main branch of gz-cmake and then building this PR.

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

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.

[scpeters]

I think we'll want to revert the gazebodistro changes back to using gz-tools2 branch for ionic files