Repository: flutter
Issue: `NestedScrollView`'s `SliverAppBar` doesn't float when body scrolled by `ScrollBar`
Labels: framework,f: scrolling,has reproducible steps,P2,found in release: 3.3,found in release: 3.6,team-framework,triaged-framework

## Steps to Reproduce

1. Execute `flutter run` on the code sample <!-- (see "Code sample" section below) -->
2. Scroll via `ScrollBar`

**Expected results:**
`SliverAppBar` starts floating just like it was dragged by touch or by mouse scroll wheel

**Actual results:**
`SliverAppBar` doesn't float

<details>
<summary>Code sample</summary>

```dart
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyScrollBehavior extends MaterialScrollBehavior {
  const MyScrollBehavior();

  @override
  Widget buildScrollbar(BuildContext context, Widget child, ScrollableDetails details) {
    // regardless of platform, always use a scrollbar
    return Scrollbar(
      controller: details.controller,
      child: child,
    );
  }

  @override
  Set<PointerDeviceKind> get dragDevices => const {...PointerDeviceKind.values};
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHome(),
      scrollBehavior: MyScrollBehavior(),
    );
  }
}

class MyHome extends StatelessWidget {
  const MyHome({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NestedScrollView(
        floatHeaderSlivers: true,
        headerSliverBuilder: (context, innerBoxIsScrolled) {
          return <Widget>[
            SliverOverlapAbsorber(
              handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context),
              sliver: SliverAppBar(
                title: const Text('SliverAppBar'),
                pinned: true,
                floating: true,
                expandedHeight: 150,
                forceElevated: innerBoxIsScrolled,
                bottom: const PreferredSize(
                  preferredSize: Size.fromHeight(50),
                  child: Text('123'),
                ),
              ),
            ),
          ];
        },
        body: const MyScrollable(),
      ),
    );
  }
}

class MyScrollable extends StatelessWidget {
  const MyScrollable({super.key});

  @override
  Widget build(BuildContext context) {
    return CustomScrollView(
      slivers: <Widget>[
        SliverOverlapInjector(
          handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context),
        ),
        SliverFixedExtentList(
          itemExtent: 48,
          delegate: SliverChildBuilderDelegate(
            childCount: 100,
            (context, index) {
              return ListTile(
                title: Text('Item $index'),
              );
            },
          ),
        ),
      ],
    );
  }
}
```

</details>

<details>
  <summary>flutter doctor -v</summary>

```
[√] Flutter (Channel stable, 3.3.8, on Microsoft Windows [Version 10.0.19044.2251], locale hu-HU)
    • Flutter version 3.3.8 on channel stable at C:\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 52b3dc25f6 (6 days ago), 2022-11-09 12:09:26 +0800
    • Engine revision 857bd6b74c
    • Dart version 2.18.4
    • DevTools version 2.15.0

[√] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
    • Android SDK at C:\Users\maRci002\AppData\Local\Android\sdk
    • Platform android-33, build-tools 33.0.0
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 11.0.13+0-b1751.21-8125866)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop for Windows (Visual Studio Community 2022 17.3.4)
    • Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
    • Visual Studio Community 2022 version 17.3.32901.215
    • Windows 10 SDK version 10.0.20348.0

[√] Android Studio (version 2021.3)
    • Android Studio at C:\Program Files\Android\Android Studio
    • 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 11.0.13+0-b1751.21-8125866)

[√] VS Code (version 1.73.1)
    • VS Code at C:\Users\maRci002\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.44.0

[√] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.19044.2251]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 107.0.5304.107
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 107.0.1418.35

[√] HTTP Host Availability
    • All required HTTP hosts are available

• No issues found!
```

</details>

**Attached video:**

1. drag :white_check_mark:
2. mouse whell :white_check_mark:
3. ScrollBar :x:

https://user-images.githubusercontent.com/8436039/201914260-6b0e5356-779e-45ad-9d1b-5bd6d8bca3da.mp4