CI: explore trigger required checks on special comment

[Borda]

🚀 Feature

How about setting that the check is run on specific comments, so the scenario would be:

• if you edit a particular codebase, your check is started automatically because of the relevance
• if your change is small, and some check was not triggered just before the merge, you may request to run these checks to satisfy and pass them as required jobs

see inspiration: https://github.com/orgs/community/discussions/25389#discussioncomment-3247738

Motivation

We would remove most of our skip hacks and kee straight reliable CI

Alternatives

find some similar solution for grouping as we had with

• Configure the check-group app #14165
• Remove skipping logic in favor of path filtering #14170
• Add a required job checker as an action (1/2) #14363, Set path filters in favor of the required-job action #14294
• ci: drop group probot #14456

cc @carmocca @akihironitta @Borda