[8.x] updatecli: use updatecli policies (backport #13934)

[mergify]

Support for the ironbank bump automation for ubi9 using updatecli.
It uses https://www.updatecli.io/blog/shareable-policies, for such I refactored the files under .ci/updatecli and the consumers. So now all the scm configuration is in the values file.

Motivation/summary

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

1. gh pr checkout 13934
2. Install updatecli
3. Login to ghcr.io
4. Diff (dry-run)

$ GITHUB_TOKEN=$(gh auth token) updatecli compose diff --experimental

5. Create Pull Request if new changes

$ GITHUB_REPOSITORY=elastic/apm-server \
   GITHUB_ACTOR=v1v \
   GITHUB_TOKEN=$(gh auth token) \
updatecli compose apply --experimental

Related issues

---

This is an automatic backport of pull request #13934 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 3351902 has failed:

On branch mergify/bp/8.x/pr-13934
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 3351902f8.
  (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)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both added:      .ci/updatecli/values.d/scm.yml
	both added:      .github/workflows/update-compose.yml
	both added:      updatecli-compose.yaml

no changes added to commit (use "git add" and/or "git commit -a")

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