Skip package-and-qa if an MR only quarantines tests

What does this MR do and why?

Checks the diffs of changed files in an MR and skips package-and-qa if there are only quarantined tests.

The pipeline will still include the package-and-qa job, but it will finish without triggering downstream pipelines.

See https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/1051

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Test MRs

MR	package-and-qa status	Success?
Only quarantine	package-and-qa did not trigger downstream pipelines	✅
Quarantine and non-quarantine test change	package-and-qa did trigger downstream pipelines	✅
Quarantine and framework change	package-and-qa did trigger downstream pipelines	✅