chore(Release Drafter) cleanup and allow manual execution

[dduportal]

This PR cleans up the release drafter workflow:

• Remove a duplicated workflow
• Switch to a reusable one
• Allow manual excution of release-drafter by add the workflow_dispatch trigger (use case: regenerate a draft changelog after adding missing labels on PRs already merged)
• Use a fixed version name (as releases of this images follow concatenation of the remoting version with a suffix build number)

[timja]

There's also a reusable one here that could be used:
https://github.com/jenkinsci/.github/blob/master/.github/workflows/release-drafter.yml

but if it's fixed to v5 here it should be fine to keep this

[dduportal]

There's also a reusable one here that could be used: https://github.com/jenkinsci/.github/blob/master/.github/workflows/release-drafter.yml

but if it's fixed to v5 here it should be fine to keep this

Oh, I did not know. Let me switch to the reusable one to avoid spreading configs.

Side note: shall we force the release draft name to something static such as next now that we are using the CD default version scheme + it's the concatenation of the remoting version with a suffix (build number)?

[timja]

Side note: shall we force the release draft name to something static such as next now that we are using the CD default version scheme + it's the concatenation of the remoting version with a suffix (build number)?

no opinion on that, either is fine