Alerting: Run state manager as regular sub-service (#58246)

pkg/services/ngalert/schedule/schedule.go

@@ -298,8 +298,6 @@ func (sch *schedule) schedulePeriodic(ctx context.Context, t *ticker.T) error {
 		case <-ctx.Done():
 			// waiting for all rule evaluation routines to stop
 			waitErr := dispatcherGroup.Wait()
-			// close the state manager and flush the state
-			sch.stateManager.Close()
 			return waitErr
 		}
 	}