Repository: flutter
Issue: [flutter_adaptive_scaffold] body overlaps topNavigation elevation shadow
Labels: package,team-ecosystem,has reproducible steps,P3,found in release: 3.3,p: flutter_adaptive_scaffold,found in release: 3.7,triaged-ecosystem

It is common to have a `topNavigation` bar that has some elevation so that it drops some shadow over the body.

I'm trying to achieve that using the `AdaptiveLayout` from the `flutter_adaptive_scaffold` package (v0.0.8). However, because the body is drawn after the topNavigation, it always overlaps the shadow.

## Steps to Reproduce

1. Add a container with elevation > 0 in `topNavigation` slot
2. Add a non-transparent `body`

**Expected results:** The elevation shadow from the `topNavigation` should drop on the body

**Actual results:** The body overlaps the shadow

![image](https://user-images.githubusercontent.com/6546265/208266289-1fe77573-7de2-406c-93a7-281c5ebb779d.png)

<details>
<summary>Code sample</summary>

```dart
import 'package:flutter/material.dart';
import 'package:flutter_adaptive_scaffold/flutter_adaptive_scaffold.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({super.key});

  @override
  Widget build(BuildContext context) {
    final List<Widget> children = List<Widget>.generate(10, (int index) {
      return Padding(
        padding: const EdgeInsets.all(8.0),
        child: Container(
          color: const Color.fromARGB(255, 255, 203, 32),
          height: 400,
        ),
      );
    });

    return ColoredBox(
      color: Colors.white,
      child: AdaptiveLayout(
        internalAnimations: false,
        topNavigation: SlotLayout(
          config: <Breakpoint, SlotLayoutConfig>{
            Breakpoints.smallAndUp: SlotLayout.from(
              key: const Key('topNavigation'),
              builder: (_) => const TopNavigationBar(),
            ),
          },
        ),
        body: SlotLayout(
          config: <Breakpoint, SlotLayoutConfig>{
            Breakpoints.smallAndUp: SlotLayout.from(
              key: const Key('body'),
              builder: (_) => Center(
                child: ConstrainedBox(
                  constraints: const BoxConstraints(maxWidth: 750),
                  child: Scaffold(
                    backgroundColor: Colors.white,
                    body: GridView.count(crossAxisCount: 2, children: children),
                  ),
                ),
              ),
            )
          },
        ),
      ),
    );
  }
}

class TopNavigationBar extends StatelessWidget {
  const TopNavigationBar({
    super.key,
  });

  @override
  Widget build(final BuildContext context) {
    return Material(
      elevation: 2,
      child: ColoredBox(
        color: Colors.white,
        child: Padding(
          padding: const EdgeInsets.symmetric(vertical: 16, horizontal: 56),
          child: Row(
            children: const <Widget>[FlutterLogo()],
          ),
        ),
      ),
    );
  }
}
```

</details>