Fix CheckRepoStats and reuse it during migration (#18264)

The CheckRepoStats function missed the following counters:

- label num_closed_issues & num_closed_pulls
- milestone num_closed_issues & num_closed_pulls

The update SQL statements for updating the repository
num_closed_issues & num_closed_pulls fields were repeated in three
functions (repo.CheckRepoStats, migrate.insertIssues and
models.Issue.updateClosedNum) and were moved to a single helper.

The UpdateRepoStats is implemented and called in the Finish migration method so that it happens immediately instead of wating for the
CheckRepoStats to run.

Signed-off-by: Loïc Dachary loic@dachary.org

---
[source](https://lab.forgefriends.org/forgefriends/forgefriends/-/merge_requests/34)

services/migrations/gitea_uploader.go

@@ -978,6 +978,10 @@ func (g *GiteaLocalUploader) Finish() error {
 		return err
 	}
 
+	if err := models.UpdateRepoStats(db.DefaultContext, g.repo.ID); err != nil {
+		return err
+	}
+
 	g.repo.Status = repo_model.RepositoryReady
 	return repo_model.UpdateRepositoryCols(g.repo, "status")
 }