feat(pipeline): allow to run on a limited plugin set

[lemeurherve]

This change allows to run on a limited plugin set via limited-plugin-set label or marker file, useful to test and verify pipeline changes and test cases without consuming too many resources.

First extract from:

• wip: costs reduction #7037

Testing done

CI

Testing when a PR has limited-plugin-set (and weekly-test FTR), failing at the end as expected due to the label still there: https://ci.jenkins.io/job/Tools/job/bom/job/PR-7077/11

Testing limited-plugin-set marker file: https://ci.jenkins.io/job/Tools/job/bom/job/PR-7077/13

$ echo 'jenkinsci/variant-plugin     variant' > limited-plugin-set
$ git add limited-plugin-set
$ git commit -m 'Run limited plugin set'

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed

[lemeurherve]

Like #7079, merging to continue on #7073 and #7037 extractions more efficiently.

I'll address any post-merge suggestion in follow-up PRs if needed.

[lemeurherve]

Like #7079, merging to continue on #7073 and #7037 extractions more efficiently.

Rollbacked for now in #7089

Ref:

• Decrease BOM costs #7073 (comment)