[9.0] (backport #282) New way of backporting to active branches using gh action

[mergify]

Thanks for contributing to Logstash! If you haven't already signed our CLA, here's a handy link: https://www.elastic.co/contributor-agreement/

Adding new way for backporting to active branches using new gh action.

---

This is an automatic backport of pull request #282 done by Mergify.

[mergify]

Cherry-pick of 0075eca has failed:

On branch mergify/bp/9.0/pr-282
Your branch is up to date with 'origin/9.0'.

You are currently cherry-picking commit 0075eca.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   .github/workflows/backport-active.yml

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   .mergify.yml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[ev1yehor]

Was created for test purposes.