feat: allow runners to request a particular job (#11676)

Forgejo Runner can optionally ask for a particular job. Example: `forgejo-runner one-job --handle 9d52c7d8-aebe-426b-b015-dd453aacaada`. This change adds the necessary job filtering to Forgejo.

See https://code.forgejo.org/forgejo/forgejo-actions-feature-requests/issues/76 for the motivation and design considerations.

PR for the extension of the runner protocol: https://code.forgejo.org/forgejo/actions-proto/pulls/18

Related change in Forgejo Runner with usage example: https://code.forgejo.org/forgejo/runner/pulls/1443

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### 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/11676): <!--number 11676 --><!--line 0 --><!--description YWxsb3cgcnVubmVycyB0byByZXF1ZXN0IGEgcGFydGljdWxhciBqb2I=-->allow runners to request a particular job<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11676
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>
Co-authored-by: Andreas Ahlenstorf <andreas@ahlenstorf.ch>
Co-committed-by: Andreas Ahlenstorf <andreas@ahlenstorf.ch>

modules/structs/action.go

@@ -14,6 +14,8 @@ type ActionRunJob struct {
 	ID int64 `json:"id"`
 	// How many times the job has been attempted including the current attempt.
 	Attempt int64 `json:"attempt"`
+	// Opaque identifier that uniquely identifies a single attempt of a job.
+	Handle string `json:"handle"`
 	// the repository id
 	RepoID int64 `json:"repo_id"`
 	// the owner id