refactor(google-maps): expose event manager (#24898)

Exposes the `MapEventManager` that we use to bind events in the Google Maps package so that users implementing their own components can consume it as well.

Author: crisbeto

src/google-maps/public-api.ts

@@ -35,3 +35,4 @@ export {
   AriaLabelFn,
   Calculator,
 } from './map-marker-clusterer/marker-clusterer-types';
+export {MapEventManager} from './map-event-manager';

tools/public_api_guard/google-maps/google-maps.md

@@ -291,6 +291,14 @@ export class MapDirectionsService {
     static ɵprov: i0.ɵɵInjectableDeclaration<MapDirectionsService>;
 }
 
+// @public
+export class MapEventManager {
+    constructor(_ngZone: NgZone);
+    destroy(): void;
+    getLazyEmitter<T>(name: string): Observable<T>;
+    setTarget(target: MapEventManagerTarget): void;
+}
+
 // @public
 export class MapGeocoder {
     constructor(_ngZone: NgZone);