feat(core): expose a Compiler API for accessing module ids from NgModule types (#24258)

This will allow RouterTestingModule to better support lazy loading of modules
when using summaries, since it can detect whether a module is already loaded
if it can access the id.

PR Close #24258

packages/platform-browser-dynamic/src/compiler_factory.ts

@@ -78,6 +78,10 @@ export class CompilerImpl implements Compiler {
   }
   clearCache(): void { this._delegate.clearCache(); }
   clearCacheFor(type: Type<any>) { this._delegate.clearCacheFor(type); }
+  getModuleId(moduleType: Type<any>): string|undefined {
+    const meta = this._metadataResolver.getNgModuleMetadata(moduleType);
+    return meta && meta.id || undefined;
+  }
 }
 
 /**