ci: skip tests if unaffected (WIP) TASK-1316

[p2edwards]

WIP rework of #5140

🗒️ Checklist

1. run linter locally
2. update all related docs (API, README, inline, etc.), if any
3. draft PR with a title <type>(<scope>)<!>: <title> TASK-1234
4. tag PR: at least frontend or backend unless it's global
5. fill in the template below and delete template comments
6. review thyself: read the diff and repro the preview as written
7. open PR & confirm that CI passes
8. request reviewers, if needed
9. delete this section before merging

👀 Preview steps

Bug template:

1. ℹ️ have an account and a project
2. do this
3. do that
4. 🔴 [on main] notice that this isn't anywhere BUT it should be here
5. 🟢 [on PR] notice that this is here

Feature/no-change template:

1. ℹ️ have account and a project
2. do this
3. do that
4. 🟢 notice that this is there
5. do that another thing
6. 🟢 notice that this changed like that

💭 Notes