feat(service-worker): handle 'notificationclick' events (#25860)

The previous version did not support the 'notificationclick' event.
Add event handler for the event and provide an observable of
clicked notifications in the SwPush service.

Closes #20956, #22311

PR Close #25860

packages/service-worker/testing/mock.ts

@@ -28,6 +28,7 @@ export class MockServiceWorkerContainer {
   mockRegistration: MockServiceWorkerRegistration|null = null;
   controller: MockServiceWorker|null = null;
   messages = new Subject();
+  messagesClicked = new Subject();
 
   addEventListener(event: 'controllerchange'|'message', handler: Function) {
     if (event === 'controllerchange') {