feat(core): make ngprobe tokens pluggable

tools/public_api_guard/platform-browser/index.d.ts

@@ -126,6 +126,11 @@ export interface MessageBusSource {
     initChannel(channel: string, runInZone: boolean): void;
 }
 
+/** @experimental */
+export declare class NgProbeToken {
+    constructor(name: string, token: any);
+}
+
 /** @experimental */
 export declare const platformBrowser: (extraProviders?: any[]) => PlatformRef;