[CP-stable]Refactor route focus node creation (#149378)

### Issue Link:
https://github.com/flutter/flutter/issues/148867

Cherry-picking https://github.com/flutter/flutter/pull/147390

### Changelog Description:
Fixes a focus issue that causes TextFields to not function after cupertino back swipes

### Impact Description:
iOS, macos, iOS web, macos web app that uses TextField

### Workaround:
disable cupertino back swipe

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
What are the steps to validate that this fix works?

TextField should not be broken after a cupertino back swipe

examples/api/test/widgets/transitions/listenable_builder.1_test.dart

@@ -10,7 +10,7 @@ void main() {
   testWidgets('Tapping FAB increments counter', (WidgetTester tester) async {
     await tester.pumpWidget(const example.ListenableBuilderExample());
 
-    String getCount() => (tester.widget(find.descendant(of: find.byType(ListenableBuilder), matching: find.byType(Text))) as Text).data!;
+    String getCount() => (tester.widget(find.descendant(of: find.byType(ListenableBuilder).last, matching: find.byType(Text))) as Text).data!;
 
     expect(find.text('Current counter value:'), findsOneWidget);
     expect(find.text('0'), findsOneWidget);

packages/flutter/lib/src/widgets/routes.dart

@@ -1022,6 +1022,8 @@ class _ModalScopeState<T> extends State<_ModalScope<T>> {
 
   @override
   Widget build(BuildContext context) {
+    // Only top most route can participate in focus traversal.
+    focusScopeNode.skipTraversal = !widget.route.isCurrent;
     return AnimatedBuilder(
       animation: widget.route.restorationScopeId,
       builder: (BuildContext context, Widget? child) {
@@ -1048,24 +1050,22 @@ class _ModalScopeState<T> extends State<_ModalScope<T>> {
                   },
                   child: PrimaryScrollController(
                     controller: primaryScrollController,
-                    child: FocusScope(
-                      node: focusScopeNode, // immutable
-                      // Only top most route can participate in focus traversal.
-                      skipTraversal: !widget.route.isCurrent,
+                    child: FocusScope.withExternalFocusNode(
+                      focusScopeNode: focusScopeNode, // immutable
                       child: RepaintBoundary(
-                        child: AnimatedBuilder(
-                          animation: _listenable, // immutable
+                        child: ListenableBuilder(
+                          listenable: _listenable, // immutable
                           builder: (BuildContext context, Widget? child) {
                             return widget.route.buildTransitions(
                               context,
                               widget.route.animation!,
                               widget.route.secondaryAnimation!,
-                              // This additional AnimatedBuilder is include because if the
+                              // This additional ListenableBuilder is include because if the
                               // value of the userGestureInProgressNotifier changes, it's
                               // only necessary to rebuild the IgnorePointer widget and set
                               // the focus node's ability to focus.
-                              AnimatedBuilder(
-                                animation: widget.route.navigator?.userGestureInProgressNotifier ?? ValueNotifier<bool>(false),
+                              ListenableBuilder(
+                                listenable: widget.route.navigator?.userGestureInProgressNotifier ?? ValueNotifier<bool>(false),
                                 builder: (BuildContext context, Widget? child) {
                                   final bool ignoreEvents = _shouldIgnoreFocusRequest;
                                   focusScopeNode.canRequestFocus = !ignoreEvents;

packages/flutter/test/widgets/routes_test.dart

@@ -1736,7 +1736,7 @@ void main() {
       semantics.dispose();
     }, variant: const TargetPlatformVariant(<TargetPlatform>{TargetPlatform.iOS}));
 
-    testWidgets('focus traverse correct when pop multiple page simultaneously', (WidgetTester tester) async {
+    testWidgets('focus traversal is correct when popping multiple pages simultaneously', (WidgetTester tester) async {
       // Regression test: https://github.com/flutter/flutter/issues/48903
       final GlobalKey<NavigatorState> navigatorKey = GlobalKey<NavigatorState>();
       await tester.pumpWidget(MaterialApp(