updatecli: use shared policy

[v1v]

What does this PR do?

Use a shared updatecli policy. The exact configuration is used in different GitHub repositories.

Already applied in the apm-agent-php, see https://github.com/elastic/apm-agent-php/pull/1188 and https://github.com/elastic/apm-agent-php/pull/1185

I ran https://github.com/elastic/apm-agent-java/actions/runs/9805677528/job/27075850294, and it worked, though all the specs are up-to-date.

Checklist

• [ ] This is an enhancement of existing features, or a new feature in existing plugins
  • [ ] I have updated CHANGELOG.asciidoc
  • [ ] I have added tests that prove my fix is effective or that my feature works
  • [ ] Added an API method or config option? Document in which version this will be introduced
  • [ ] I have made corresponding changes to the documentation
• [ ] This is a bugfix
  • [ ] I have updated CHANGELOG.asciidoc
  • [ ] I have added tests that would fail without this fix
• [ ] This is a new plugin
  • [ ] I have updated CHANGELOG.asciidoc
  • [ ] My code follows the style guidelines of this project
  • [ ] I have made corresponding changes to the documentation
  • [ ] I have added tests that prove my fix is effective or that my feature works
  • [ ] New and existing unit tests pass locally with my changes
  • [ ] I have updated supported-technologies.asciidoc
  • [ ] Added an API method or config option? Document in which version this will be introduced
  • [ ] Added an instrumentation plugin? Describe how you made sure that old, non-supported versions are not instrumented by accident.
• [ ] This is something else
  • [ ] I have updated CHANGELOG.asciidoc