perf(angular): bundle size improvements for angular (#16966)

angular/src/providers/alert-controller.ts

@@ -3,7 +3,9 @@ import { AlertOptions } from '@ionic/core';
 
 import { OverlayBaseController } from '../util/overlay';
 
-@Injectable()
+@Injectable({
+  providedIn: 'root',
+})
 export class AlertController extends OverlayBaseController<AlertOptions, HTMLIonAlertElement> {
   constructor() {
     super('ion-alert-controller');