Replace navigation_and_routing with a new sample (#832)

* move snippets into old_snippets directory

* add new navigation_and_routing sample

* add copyright headers

* Apply #827 to old_snippets/ directory and upgrade them to null safety

* Code review comments

- Move Guard class into parser.dart
- Move usage of guards from Delegate to RouteInformationParser
- Rename delegate to SimpleRouterDelegate

* clean up imports

* refactor settings screen, fix bug

* avoid conflicting paths /books/new and /books/1 - rename to book/1

* dispose fields in _BookstoreState class

* remove /books path

This was causing problems

* add comment

* Change BookstoreAuthScope and BookstoreAuthScope to InheritedNotifier

* fix warnings

* Make the initial route configurable, set to '/signin'

* Enable deep linking

https://flutter.dev/docs/development/ui/navigation/deep-linking

* use path URL strategy on the web.

* remove TODO, add comment

navigation_and_routing/pubspec.yaml

@@ -1,20 +1,23 @@
-name: navigation_and_routing
-description: Navigation and routing samples
-publish_to: 'none'
-
+name: bookstore
+description: Navigation and routing sample app
+publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 version: 1.0.0+1
-
 environment:
-  sdk: ">=2.10.0 <3.0.0"
-
+  sdk: ">=2.12.0 <3.0.0"
 dependencies:
   flutter:
     sdk: flutter
-  cupertino_icons: ^1.0.0
-
+  cupertino_icons: ^1.0.2
+  quiver: ^3.0.0
+  path_to_regexp: ^0.4.0
+  adaptive_navigation: ^0.0.3
+  collection: ^1.15.0
+  url_launcher: ^6.0.0
+  url_strategy: ^0.2.0
 dev_dependencies:
+  test: ^1.16.0
   flutter_test:
     sdk: flutter
-
+  flutter_lints: ^1.0.0
 flutter:
   uses-material-design: true