feat: expose attempt number of ActionRunJob in HTTP API (#11687)

Expose the attempt number of `ActionRunJob` in the HTTP API. It is required to uniquely identify a job run.

Example:

```
$ curl -u andreas --basic http://192.168.178.62:3000/api/v1/repos/andreas/test/actions/runners/jobs
```
```json
[{"id":63,"attempt":2,"repo_id":1,"owner_id":1,"name":"test","needs":null,"runs_on":["debian"],"task_id":0,"status":"waiting"}]
```

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### Tests for Go changes

(can be removed for JavaScript changes)

- I added test coverage for Go changes...
  - [ ] 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.
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Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11687
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

@@ -10,8 +10,10 @@ import (
 // ActionRunJob represents a job of a run
 // swagger:model
 type ActionRunJob struct {
-	// the action run job id
+	// Identifier of this job.
 	ID int64 `json:"id"`
+	// How many times the job has been attempted including the current attempt.
+	Attempt int64 `json:"attempt"`
 	// the repository id
 	RepoID int64 `json:"repo_id"`
 	// the owner id