refactor(docs-infra): extract all lazy-loading-ngmodules examples from mini-app (#34599)

Previously, some of the examples in the `lazy-loading-ngmodules` guide
were hard-coded.

This commit ensures all examples in the guide are extracted from
docregions in the corresponding example project.

PR Close #34599

aio/content/examples/lazy-loading-ngmodules/src/app/app-routing.module.ts

@@ -4,23 +4,26 @@ import { NgModule } from '@angular/core';
 import { Routes, RouterModule } from '@angular/router';
 
 
-// #docregion const-routes
+// #docregion const-routes, routes-customers, routes-customers-orders
 const routes: Routes = [
   {
     path: 'customers',
     loadChildren: () => import('./customers/customers.module').then(mod => mod.CustomersModule)
+    // #enddocregion routes-customers
   },
   {
     path: 'orders',
     loadChildren: () => import('./orders/orders.module').then(mod => mod.OrdersModule)
+    // #enddocregion routes-customers-orders
   },
   {
     path: '',
     redirectTo: '',
     pathMatch: 'full'
+    // #docregion routes-customers, routes-customers-orders
   }
 ];
-// #enddocregion const-routes
+// #enddocregion const-routes, routes-customers, routes-customers-orders
 
 @NgModule({
   imports: [