test(angular): add a landing page to go between lazy and standalone apps (#30286)

## What is the new behavior?
Adds a landing page to the Angular test app to make it easier to get to
and debug standalone.

## Does this introduce a breaking change?
- [ ] Yes
- [x] No

Co-authored-by: Brandy Smith <6577830+brandyscarney@users.noreply.github.com>

packages/angular/test/base/src/app/app.routes.ts

@@ -1,16 +1,18 @@
 import { Routes } from '@angular/router';
+import { AppLandingComponent } from './app-landing/app-landing.component';
 
 export const routes: Routes = [
   {
     path: '',
     pathMatch: 'full',
-    /**
-     * Omit the slash at the beginning
-     * so query params are preserved.
-     * https://github.com/angular/angular/issues/13315#issuecomment-427254639
-     */
-    redirectTo: 'lazy'
+    component: AppLandingComponent
   },
-  { path: 'lazy', loadChildren: () => import('./lazy/app-lazy/app.module').then(m => m.AppModule) },
-  { path: 'standalone', loadChildren: () => import('./standalone/app-standalone/app.routes').then(m => m.routes) }
+  {
+    path: 'lazy',
+    loadChildren: () => import('./lazy/app-lazy/app.module').then(m => m.AppModule)
+  },
+  {
+    path: 'standalone',
+    loadChildren: () => import('./standalone/app-standalone/app.routes').then(m => m.routes)
+  }
 ];