Separate galactic branch from ros2 branch

[chapulina]

🎉 New feature

• Part of Branch off for Galactic #200

Summary

I just created the galactic branch off ros2. This PR removes Rolling support from this branch.

We haven't been officially supporting Citadel and Fortress with Galactic, but since it may have been working from source all along, rather than removing these I enabled CI for them. If CI comes back broken, I'll remove support for them unless someone has a need for it.

Test it

Let's see CI results.

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• 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.

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[chapulina]

Citadel fails to build. So it's safe to assume no one is counting on it. Removed in ff347d8