Update navigation_and_routing sample to go_router (#2067)

This is a new PR to update the navigation_and_routing sample to the
latest version of go_router. It is a based on
https://github.com/flutter/samples/pull/1437

---------

Co-authored-by: Brett Morgan <brettmorgan@google.com>

navigation_and_routing/lib/src/screens/authors.dart

@@ -4,14 +4,19 @@
 
 import 'package:flutter/material.dart';
 
+import '../data/author.dart';
 import '../data/library.dart';
-import '../routing.dart';
 import '../widgets/author_list.dart';
 
 class AuthorsScreen extends StatelessWidget {
-  final String title = 'Authors';
+  final String title;
+  final ValueChanged<Author> onTap;
 
-  const AuthorsScreen({super.key});
+  const AuthorsScreen({
+    required this.onTap,
+    this.title = 'Authors',
+    super.key,
+  });
 
   @override
   Widget build(BuildContext context) => Scaffold(
@@ -20,9 +25,7 @@ class AuthorsScreen extends StatelessWidget {
         ),
         body: AuthorList(
           authors: libraryInstance.allAuthors,
-          onTap: (author) {
-            RouteStateScope.of(context).go('/author/${author.id}');
-          },
+          onTap: onTap,
         ),
       );
 }