CI: split [oc.misc_checks]

What

Splits the job [oc.misc_checks] into smaller pieces that run depending on what changes: in a given merge request.

Why

This job takes 5 minutes which is annoying in the cases it's the only job running. Misc checks is also one of the typical jobs that fail in marge-bot pipelines, so having early failures there is also pleasant for Developer Experience.

How

Nothing to it.

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR