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)

models/issue_lock.go

@@ -46,7 +46,7 @@ func updateIssueLock(opts *IssueLockOptions, lock bool) error {
 	}
 	defer committer.Close()
 
-	if err := updateIssueCols(db.GetEngine(ctx), opts.Issue, "is_locked"); err != nil {
+	if err := updateIssueCols(ctx, opts.Issue, "is_locked"); err != nil {
 		return err
 	}