refactor(core): change module semantics

This contains major changes to the compiler, bootstrap of the platforms
and test environment initialization.

Main part of #10043
Closes #10164

BREAKING CHANGE:
- Semantics and name of `@AppModule` (now `@NgModule`) changed quite a bit.
  This is actually not breaking as `@AppModules` were not part of rc.4.
  We will have detailed docs on `@NgModule` separately.
- `coreLoadAndBootstrap` and `coreBootstrap` can't be used any more (without migration support).
  Use `bootstrapModule` / `bootstrapModuleFactory` instead.
- All Components listed in routes have to be part of the `declarations` of an NgModule.
  Either directly on the bootstrap module / lazy loaded module, or in an NgModule imported by them.

tools/public_api_guard/router/index.d.ts

@@ -135,7 +135,7 @@ export declare class Router {
     /** @experimental */ navigated: boolean;
     routerState: RouterState;
     url: string;
-    constructor(rootComponentType: Type, resolver: ComponentResolver, urlSerializer: UrlSerializer, outletMap: RouterOutletMap, location: Location, injector: Injector, loader: AppModuleFactoryLoader, config: Routes);
+    constructor(rootComponentType: Type, resolver: ComponentResolver, urlSerializer: UrlSerializer, outletMap: RouterOutletMap, location: Location, injector: Injector, loader: NgModuleFactoryLoader, config: Routes);
     createUrlTree(commands: any[], {relativeTo, queryParams, fragment, preserveQueryParams, preserveFragment}?: NavigationExtras): UrlTree;
     dispose(): void;
     initialNavigation(): void;
@@ -203,6 +203,10 @@ export declare class RouterModule {
     constructor(injector: Injector);
 }
 
+/** @experimental */
+export declare class RouterModuleWithoutProviders {
+}
+
 /** @stable */
 export declare class RouterOutlet {
     activateEvents: EventEmitter<any>;