Refactor commit status for Actions jobs (#23786)

Before:
<img width="353" alt="xnip_230329_163852"
src="https://user-images.githubusercontent.com/9418365/228479807-424452df-10fa-45cf-ae4b-09939c0ed54c.png">
After:
<img width="508" alt="xnip_230329_163358"
src="https://user-images.githubusercontent.com/9418365/228479923-537b54fe-9564-4105-a068-bcc75fa2a7ea.png">

Highlights:
- Treat `StatusSkipped` as `CommitStatusSuccess` instead of
`CommitStatusFailure`, so it fixed #23599.
- Use the bot user `gitea-actions` instead of the trigger as the creator
of commit status.
- New format `<run_name> / <job_name> / (<event>)` for the context of
commit status to avoid conflicts.
- Add descriptions for commit status.
- Add the missing calls to `CreateCommitStatus`.
- Refactor `CreateCommitStatus` to make it easier to use.

routers/api/actions/runner/runner.go

@@ -149,10 +149,7 @@ func (s *Service) UpdateTask(
 		return nil, status.Errorf(codes.Internal, "load job: %v", err)
 	}
 
-	if err := actions_service.CreateCommitStatus(ctx, task.Job); err != nil {
-		log.Error("Update commit status for job %v failed: %v", task.Job.ID, err)
-		// go on
-	}
+	actions_service.CreateCommitStatus(ctx, task.Job)
 
 	if req.Msg.State.Result != runnerv1.Result_RESULT_UNSPECIFIED {
 		if err := actions_service.EmitJobsIfReady(task.Job.RunID); err != nil {