Use Ruby code to determine which migrations to run

What does this Merge Request do?

⚠ This MR needs !1468 (merged) (I can't seem to add as a MR dependency?)

⚠ This MR needs !1490 (merged) (I can't seem to add as a MR dependency?)

The solution in !1407 (merged) works, but it ain't pretty. It will also be hard to maintain.

So instead this introduces the same logic, but nicer written in Ruby code.

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.