ci(docker-nightly): move to separate build/publish from test

[TheGreatRefrigerator]

previously the nightly build was not built nightly but on many changes in PRs as well.
This is now moved to a separate workflow that runs nightly, with workflow_dispatch option to build images for different branches & repos on demand.

Pull Request Checklist

• 1. I have rebased the latest version of the main branch into my feature branch and all conflicts
  have been resolved.
• 2. I have added information about the change/addition to functionality to the CHANGELOG.md file under the
  [Unreleased] heading.
• 3. I have documented my code using JDocs tags.
• 4. I have removed unnecessary commented out code, imports and System.out.println statements.
• 5. I have written JUnit tests for any new methods/classes and ensured that they pass.
• 6. I have created API tests for any new functionality exposed to the API.
• 7. If changes/additions are made to the ors-config.json file, I have added these to the ors config documentation
  along with a short description of what it is for, and documented this in the Pull Request (below).
• 8. I have built graphs with my code of the Heidelberg.osm.gz file and run the api-tests with all test passing
• 9. I have referenced the Issue Number in the Pull Request (if the changes were from an issue).
• 10. For new features or changes involving building of graphs, I have tested on a larger dataset
  (at least Germany), and the graphs build without problems (i.e. no out-of-memory errors).
• 11. For new features or changes involving the graphbuilding process (i.e. changing encoders, updating the
  importer etc.), I have generated longer distance routes for the affected profiles with different options
  (avoid features, max weight etc.) and compared these with the routes of the same parameters and start/end
  points generated from the current live ORS.
  If there are differences then the reasoning for these MUST be documented in the pull request.
• 12. I have written in the Pull Request information about the changes made including their intended usage
  and why the change was needed.
• 13. For changes touching the API documentation, I have tested that the API playground renders correctly.

Fixes #1686

Information about the changes

• Key functionality added: real nightly build
• Reason for change: nightly was not built nightly

Examples and reasons for differences between live ORS routes, and those generated from this pull request

Required changes to ors config (if applicable)

[TheGreatRefrigerator]

The check for new commits doesn't work properly yet

[jhaeu]

LGTM, wc -l is just a suggesten