Core: add active users stat (#22563)

* Stats: add active user count query

* License: add info in settings

* Stats: Retrieve active users stats for different roles

+ Clean files and tests

* Stats: add dialect.Quote in queries

* Stats: improve tests (require instead of assert)

* Stats: improve tests (require instead of assert)

pkg/models/stats.go

@@ -89,3 +89,14 @@ type SystemUserCountStats struct {
 type GetSystemUserCountStatsQuery struct {
 	Result *SystemUserCountStats
 }
+
+type ActiveUserStats struct {
+	ActiveUsers   int64
+	ActiveAdmins  int64
+	ActiveEditors int64
+	ActiveViewers int64
+}
+
+type GetActiveUserStatsQuery struct {
+	Result *ActiveUserStats
+}