Fix Router Config Issues #4300 (go_router_builder/example) (#4369)

This PR is an extension of the previous PR #4300 that I submitted. The previous PR, being based on the main branch, was closed and the contents were copied to a new branch in order to make further contributions.�

In the previous PR, an assertion error was fixed by adding `routeInformationProvider` to `MaterialApp.router`. After a series of code reviews, we updated to use routerConfig and added some test codes.

All the contents have been transferred to the current `bugfix/RouterConfig` branch.

---
*Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.*

*List which issues are fixed by this PR. You must list at least one issue.*

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*

packages/go_router_builder/example/lib/all_types.dart

@@ -550,9 +550,7 @@ class AllTypesApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) => MaterialApp.router(
-        routeInformationParser: _router.routeInformationParser,
-        routerDelegate: _router.routerDelegate,
-        routeInformationProvider: _router.routeInformationProvider,
+        routerConfig: _router,
       );
 
   late final GoRouter _router = GoRouter(

packages/go_router_builder/example/lib/main.dart

@@ -26,9 +26,7 @@ class App extends StatelessWidget {
   Widget build(BuildContext context) => ChangeNotifierProvider<LoginInfo>.value(
         value: loginInfo,
         child: MaterialApp.router(
-          routeInformationParser: _router.routeInformationParser,
-          routerDelegate: _router.routerDelegate,
-          routeInformationProvider: _router.routeInformationProvider,
+          routerConfig: _router,
           title: title,
           debugShowCheckedModeBanner: false,
         ),

packages/go_router_builder/example/lib/simple_example.dart

@@ -18,8 +18,7 @@ class App extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) => MaterialApp.router(
-        routeInformationParser: _router.routeInformationParser,
-        routerDelegate: _router.routerDelegate,
+        routerConfig: _router,
         title: _appTitle,
       );
 

packages/go_router_builder/example/test/simple_example_test.dart

@@ -0,0 +1,20 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:go_router_builder_example/shared/data.dart';
+import 'package:go_router_builder_example/simple_example.dart';
+
+void main() {
+  testWidgets('App starts on HomeScreen and displays families',
+      (WidgetTester tester) async {
+    await tester.pumpWidget(App());
+    expect(find.byType(HomeScreen), findsOneWidget);
+    expect(find.byType(ListTile), findsNWidgets(familyData.length));
+    for (final Family family in familyData) {
+      expect(find.text(family.name), findsOneWidget);
+    }
+  });
+}