Added checks for migration downtime

What does this MR do?

This adds a set of checks that check/list which migrations require downtime (or not). It also comes with a CI task that fails should a migration not be tagged properly.

Are there points in the code the reviewer needs to double check?

Everything.

Why was this MR needed?

Right now there's no indication of which migrations require downtime. As a result of this a release manager has to manually verify every migration.

What are the relevant issue numbers?

Fixes #14545 (closed)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added Internal change
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together