fix(service-worker): allow disabling SW while still using services

Currently, the way to not use the SW is to not install its module.
However, this means that you can't inject any of its services.

This change adds a ServiceWorkerModule.disabled() MWP, that still
registers all of the right providers but acts as if the browser does
not support Service Workers.

tools/public_api_guard/service-worker/service-worker.d.ts

@@ -1,6 +1,9 @@
 /** @experimental */
 export declare class ServiceWorkerModule {
-    static register(script: string, opts?: RegistrationOptions): ModuleWithProviders;
+    static register(script: string, opts?: {
+        scope?: string;
+        enabled?: boolean;
+    }): ModuleWithProviders;
 }
 
 /** @experimental */