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/core/src/linker/compiler.ts

@@ -78,6 +78,11 @@ export class Compiler {
    * Clears the cache for the given component/ngModule.
    */
   clearCacheFor(type: Type<any>) {}
+
+  /**
+   * Returns the id for a given NgModule, if one is defined and known to the compiler.
+   */
+  getModuleId(moduleType: Type<any>): string|undefined { return undefined; }
 }
 
 /**