fix(angular): support angular lazy routes in preview

[DimitarTachev]

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What is the current behavior?

When an Angular app with lazy routes is run with preview, all Angular dependencies are marked as external and the app crashes runtime because the @angular/core NgModuleFactoryLoader is located in node_modules and it's not able to load the lazy routes from inside the app bundle.

What is the new behavior?

When @angular/core is an external module, a new ng-replace-lazy-loader transformer is added to the @ngtools/webpack platformTransformers. It modifies the main Angular module by including and providing a local NgModuleFactoryLoader.

In this way, when an Angular app with lazy routes is run with preview, it gets a local NgModuleFactoryLoader implementation inside the app bundle allowing it to access and load the lazy routes.

Related to: NativeScript/nativescript-cli#4024