updatecli: use updatecli policies

[v1v]

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

[mergify]

This pull request does not have a backport label. Could you fix it @v1v? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.

NOTE: backport-skip has been added to this pull request.

[mergify]

backport-8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label.