Fix ExpansionTile Expanded/Collapsed announcement is interrupted by VoiceOver (#143936)

fixes [`ExpansionTile` accessibility information doesn't read Expanded/Collapsed (iOS)](https://github.com/flutter/flutter/issues/132264)

### Code sample

<details>
<summary>expand to view the code sample</summary> 

```dart
import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          title: const Text('ExpansionTile'),
        ),
        body: const ExpansionTile(
          title: Text("Title"),
          children: <Widget>[
            Placeholder(),
          ],
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () {},
          child: const Icon(Icons.add),
        ),
      ),
    );
  }
}
```

</details>

### Before

https://github.com/flutter/flutter/assets/48603081/542d8392-52dc-4319-92ba-215a7164db49

### After

https://github.com/flutter/flutter/assets/48603081/c9225144-4c12-4e92-bc41-4ff82b370ad7

packages/flutter/lib/src/material/expansion_tile.dart

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 
@@ -571,6 +574,7 @@ class _ExpansionTileState extends State<ExpansionTile> with SingleTickerProvider
 
   bool _isExpanded = false;
   late ExpansionTileController _tileController;
+  Timer? _timer;
 
   @override
   void initState() {
@@ -597,6 +601,8 @@ class _ExpansionTileState extends State<ExpansionTile> with SingleTickerProvider
   void dispose() {
     _tileController._state = null;
     _animationController.dispose();
+    _timer?.cancel();
+    _timer = null;
     super.dispose();
   }
 
@@ -621,7 +627,19 @@ class _ExpansionTileState extends State<ExpansionTile> with SingleTickerProvider
       PageStorage.maybeOf(context)?.writeState(context, _isExpanded);
     });
     widget.onExpansionChanged?.call(_isExpanded);
-    SemanticsService.announce(stateHint, textDirection);
+
+    if (defaultTargetPlatform == TargetPlatform.iOS) {
+      // TODO(tahatesser): This is a workaround for VoiceOver interrupting
+      // semantic announcements on iOS. https://github.com/flutter/flutter/issues/122101.
+      _timer?.cancel();
+      _timer = Timer(const Duration(seconds: 1), () {
+        SemanticsService.announce(stateHint, textDirection);
+        _timer?.cancel();
+        _timer = null;
+      });
+    } else {
+      SemanticsService.announce(stateHint, textDirection);
+    }
   }
 
   void _handleTap() {

packages/flutter/test/material/expansion_tile_test.dart

@@ -7,6 +7,7 @@
 @Tags(<String>['reduced-test-set'])
 library;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -788,7 +789,41 @@ void main() {
     // "Collapsed".
     expect(tester.takeAnnouncements().first.message, localizations.expandedHint);
     handle.dispose();
-  });
+  }, skip: defaultTargetPlatform == TargetPlatform.iOS); // [intended] https://github.com/flutter/flutter/issues/122101.
+
+  // This is a regression test for https://github.com/flutter/flutter/issues/132264.
+  testWidgets('ExpansionTile Semantics announcement is delayed on iOS', (WidgetTester tester) async {
+    final SemanticsHandle handle = tester.ensureSemantics();
+    const DefaultMaterialLocalizations localizations = DefaultMaterialLocalizations();
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Material(
+          child: ExpansionTile(
+            title: Text('Title'),
+            children: <Widget>[
+              SizedBox(height: 100, width: 100),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    // There is no semantics announcement without tap action.
+    expect(tester.takeAnnouncements(), isEmpty);
+
+    // Tap the title to expand ExpansionTile.
+    await tester.tap(find.text('Title'));
+    await tester.pump(const Duration(seconds: 1)); // Wait for the announcement to be made.
+
+    expect(tester.takeAnnouncements().first.message, localizations.collapsedHint);
+
+    // Tap the title to collapse ExpansionTile.
+    await tester.tap(find.text('Title'));
+    await tester.pump(const Duration(seconds: 1)); // Wait for the announcement to be made.
+
+    expect(tester.takeAnnouncements().first.message, localizations.expandedHint);
+    handle.dispose();
+  }, variant: TargetPlatformVariant.only(TargetPlatform.iOS));
 
   testWidgets('Semantics with the onTapHint is an ancestor of ListTile', (WidgetTester tester) async {
     // This is a regression test for https://github.com/flutter/flutter/pull/121624