Database: Adds new indices to alert_notification_state and alert_rule_tag tables (#28166)

Add non-unique indices to alert_notification_state and alert_rule_tag tables for 
column alert_id.

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

Fixes #22890

pkg/services/sqlstore/migrations/alert_mig.go

@@ -175,4 +175,12 @@ func addAlertMigrations(mg *Migrator) {
 	// change column type of alert.settings
 	mg.AddMigration("alter alert.settings to mediumtext", NewRawSqlMigration("").
 		Mysql("ALTER TABLE alert MODIFY settings MEDIUMTEXT;"))
+
+	mg.AddMigration("Add non-unique index alert_notification_state_alert_id", NewAddIndexMigration(alert_notification_state, &Index{
+		Cols: []string{"alert_id"}, Type: IndexType,
+	}))
+
+	mg.AddMigration("Add non-unique index alert_rule_tag_alert_id", NewAddIndexMigration(alertRuleTagTable, &Index{
+		Cols: []string{"alert_id"}, Type: IndexType,
+	}))
 }