feat: make it possible to remove workflow runs (#12478)

Add the ability to remove workflow runs, either using the UI or the HTTP API. Workflow runs can only be removed once a workflow run has completed. For security reasons, only a repository administrator or a token with `write:repository` permissions can remove runs.

Resolves https://codeberg.org/forgejo/forgejo/issues/2184.

## Checklist

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### Tests for Go changes

(can be removed for JavaScript changes)

- I added test coverage for Go changes...
  - [x] in their respective `*_test.go` for unit tests.
  - [x] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I ran...
  - [x] `make pr-go` before pushing

### Tests for JavaScript changes

(can be removed for Go changes)

- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [x] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
- [ ] This change is not visible to a Forgejo user or admin (refactor, dependency upgrade, etc.). I think there is no need to add a release note for this change.

*The decision if the pull request will be shown in the release notes is up to the mergers / release team.*

The content of the `release-notes/<pull request number>.md` file will serve as the basis for the release notes. If the file does not exist, the title of the pull request will be used instead.

<!--start release-notes-assistant-->

## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Features
  - [PR](https://codeberg.org/forgejo/forgejo/pulls/12478): <!--number 12478 --><!--line 0 --><!--description bWFrZSBpdCBwb3NzaWJsZSB0byByZW1vdmUgd29ya2Zsb3cgcnVucw==-->make it possible to remove workflow runs<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12478
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>

models/actions/run_job.go

@@ -365,3 +365,10 @@ func (job *ActionRunJob) AllNeedsExist(allExistingJobIDs container.Set[string])
 
 	return unknownJobIDs, len(unknownJobIDs) == 0
 }
+
+// DeleteJob removes the given job. Removing all associated tasks is up to the caller. If the given job does not exist,
+// nothing happens.
+func DeleteJob(ctx context.Context, jobID int64) error {
+	_, err := db.GetEngine(ctx).Delete(&ActionRunJob{ID: jobID})
+	return err
+}