fix(common): prevent duplicate URL change notifications (#37459)

Prevent duplicate notifications from being emitted when multiple URL change listeners are registered using SpyLocation#onUrlChange.

Use `@internal` annotation for the `_urlChangeSubscription` properties instead of the `private` access modifier. Otherwise, we get in trouble because of  `SpyLocation implements Location`.

PR Close #37459

packages/common/src/location/location.ts

@@ -64,7 +64,8 @@ export class Location {
   _platformLocation: PlatformLocation;
   /** @internal */
   _urlChangeListeners: ((url: string, state: unknown) => void)[] = [];
-  private _urlChangeSubscription?: SubscriptionLike;
+  /** @internal */
+  _urlChangeSubscription?: SubscriptionLike;
 
   constructor(platformStrategy: LocationStrategy, platformLocation: PlatformLocation) {
     this._platformStrategy = platformStrategy;