[PORT] Added default sorting milestones by name (gitea#27084)

Resolves https://github.com/go-gitea/gitea/issues/26996
Added default sorting for milestones by name.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

---

Conflict resolution: trivial, was due to the improvement made to 'the due
date sorting' strings.

(cherry picked from commit e8d4b7a8b198eca3b0bd117efb422d7d7cac93fe)

models/issues/milestone_list.go

@@ -70,8 +70,10 @@ func (opts FindMilestoneOptions) ToOrders() string {
 		return "num_issues DESC"
 	case "id":
 		return "id ASC"
+	case "name":
+		return "name DESC"
 	default:
-		return "deadline_unix ASC, id ASC"
+		return "deadline_unix ASC, name ASC"
 	}
 }