Repository: flutter
Issue: [web][a11y] Screen reader doesn't voice information about the list and the number of items
Labels: framework,a: accessibility,f: scrolling,has reproducible steps,P1,team-web,triaged-web,found in release: 3.19,found in release: 3.21

### Steps to reproduce

1. Execute `flutter run -d chrome` on the code sample.
2. On web, use a screen reader to read the elements.

### Expected results

1. Items are grouped into a list. 
2. The list is voiced with the number of items.
3. When moving through the elements, its index is voiced.

### Actual results

1. Items are not included in the list.
2. Each item as a separate empty group. 

### Code sample

<details open><summary>Code sample</summary>

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

void main() {
  runApp(const MyApp());
  SemanticsBinding.instance.ensureSemantics();
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Material(
        child: Scaffold(
          appBar: AppBar(backgroundColor: Colors.blue),
          body: ListView(
            semanticChildCount: 3,
            padding: const EdgeInsets.all(20.0),
            children: const [
              Text('Text 1'),
              Text('Text 2'),
              Text('Text 3'),
            ],
          ),
        ),
      ),
    );
  }
}
```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

Here is an example of how it looks:
<img width="1228" alt="Screenshot 2024-03-12 at 2 30 40 PM" src="https://github.com/flutter/flutter/assets/61043519/ce4f3373-43de-4b49-ad3c-1bcc2ecbb150">

https://github.com/flutter/flutter/assets/61043519/04caeaf2-0d1c-4a09-a8b6-ff335ccbb55c



Here is an example of what I need:
<img width="1231" alt="Screenshot 2024-03-12 at 2 31 19 PM" src="https://github.com/flutter/flutter/assets/61043519/ae018123-1581-40ba-bf7f-fdb7cbd7ef39">

https://github.com/flutter/flutter/assets/61043519/6e58ce4e-ac7f-4ad1-b81d-709d53242161
</details>


### Logs

<details open><summary>Logs</summary>

```console
[Paste your logs here]
```

</details>


### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
[✓] Flutter (Channel stable, 3.19.3, on macOS 14.3.1 23D60 darwin-x64, locale en-GB)
    • Flutter version 3.19.3 on channel stable at /Users/oleh.lysenko/development/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision ba39319843 (5 days ago), 2024-03-07 15:22:21 -0600
    • Engine revision 2e4ba9c6fb
    • Dart version 3.3.1
    • DevTools version 2.31.1

[✓] Android toolchain - develop for Android devices (Android SDK version 31.0.0)
    • Android SDK at /Users/oleh.lysenko/Library/Android/sdk
    • Platform android-33, build-tools 31.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7590822)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 15.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 15C65
    • CocoaPods version 1.14.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2021.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7590822)

[✓] Android Studio (version 2020.3)
    • Android Studio at /Users/oleh.lysenko/Library/Application Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/203.7784292/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.10+0-b96-7281165)

[✓] VS Code (version 1.67.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.60.0

[✓] Connected device (4 available)            
    • iPad (mobile)      • 00008103-001A6936112B401E            • ios            • iOS 17.3.1 21D61
    • iPhone 15 (mobile) • FEA1C1BB-BC7D-4C29-968A-FE7D45A7C3A8 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-17-2 (simulator)
    • macOS (desktop)    • macos                                • darwin-x64     • macOS 14.3.1 23D60 darwin-x64
    • Chrome (web)       • chrome                               • web-javascript • Google Chrome 122.0.6261.112

[✓] Network resources
    • All expected network resources are available.

• No issues found!
```

</details>


https://api.flutter.dev/flutter/widgets/SliverMultiBoxAdaptorWidget-class.html
| OS | role |
|--------|--------|
| web | list |
| ios | - |
| macos |  NSAccessibilityListRole |
| windows | ROLE_SYSTEM_LIST |
| android | - | 


https://api.flutter.dev/flutter/widgets/SliverChildDelegate/build.html
| OS | role |
|--------|--------|
| web | listitem |
| ios | - |
| macos | - |
| windows | ROLE_SYSTEM_LISTITEM |
| android | - |