Move examples to `ListenableBuilder` (#130671)

Updates examples to use the new `ListenableBuilder` if there's no animation. This is slightly more idiomatic.

examples/api/lib/services/keyboard_key/logical_keyboard_key.0.dart

@@ -74,8 +74,8 @@ class _MyKeyExampleState extends State<MyKeyExample> {
         child: Focus(
           focusNode: _focusNode,
           onKey: _handleKeyEvent,
-          child: AnimatedBuilder(
-            animation: _focusNode,
+          child: ListenableBuilder(
+            listenable: _focusNode,
             builder: (BuildContext context, Widget? child) {
               if (!_focusNode.hasFocus) {
                 return GestureDetector(

examples/api/lib/services/keyboard_key/physical_keyboard_key.0.dart

@@ -74,8 +74,8 @@ class _MyPhysicalKeyExampleState extends State<MyPhysicalKeyExample> {
         child: Focus(
           focusNode: _focusNode,
           onKey: _handleKeyEvent,
-          child: AnimatedBuilder(
-            animation: _focusNode,
+          child: ListenableBuilder(
+            listenable: _focusNode,
             builder: (BuildContext context, Widget? child) {
               if (!_focusNode.hasFocus) {
                 return GestureDetector(

examples/api/lib/widgets/actions/actions.0.dart

@@ -91,8 +91,8 @@ class _SaveButtonState extends State<SaveButton> {
 
   @override
   Widget build(BuildContext context) {
-    return AnimatedBuilder(
-      animation: widget.valueNotifier,
+    return ListenableBuilder(
+      listenable: widget.valueNotifier,
       builder: (BuildContext context, Widget? child) {
         return TextButton.icon(
           icon: const Icon(Icons.save),
@@ -146,8 +146,8 @@ class _ActionsExampleState extends State<ActionsExample> {
                       Actions.invoke(context, ModifyIntent(++count));
                     },
                   ),
-                  AnimatedBuilder(
-                      animation: model.data,
+                  ListenableBuilder(
+                      listenable: model.data,
                       builder: (BuildContext context, Widget? child) {
                         return Padding(
                           padding: const EdgeInsets.all(8.0),

examples/api/lib/widgets/shortcuts/shortcuts.1.dart

@@ -100,8 +100,8 @@ class _ShortcutsExampleState extends State<ShortcutsExample> {
             children: <Widget>[
               const Text('Add to the counter by pressing the up arrow key'),
               const Text('Subtract from the counter by pressing the down arrow key'),
-              AnimatedBuilder(
-                animation: model,
+              ListenableBuilder(
+                listenable: model,
                 builder: (BuildContext context, Widget? child) {
                   return Text('count: ${model.count}');
                 },