Taha Tesser 9a2d94ed8c
Fix DateRangePickerDialog does not use rangePickerHeaderBackgroundColor from DatePickerTheme in M2 (#147370)
fixes [DatePickerThemeData's `rangePickerHeaderBackgroundColor` not being applied to DateRangePickerDialog on M2](https://github.com/flutter/flutter/issues/147301)

### 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,
      theme: ThemeData(
        useMaterial3: false,
        datePickerTheme: const DatePickerThemeData(
          rangePickerHeaderBackgroundColor: Colors.red,
        ),
      ),
      home: Scaffold(
        body: Center(
          child: Builder(builder: (BuildContext context) {
            return ElevatedButton(
              onPressed: () {
                showDateRangePicker(
                  context: context,
                  currentDate: DateTime.now(),
                  initialDateRange: DateTimeRange(
                    start: DateTime.now(),
                    end: DateTime.now().add(const Duration(days: 7)),
                  ),
                  firstDate: DateTime(2000),
                  lastDate: DateTime(2025),
                );
              },
              child: const Text('Show Date Range Picker'),
            );
          }),
        ),
      ),
    );
  }
}
```

</details>

### When using `rangePickerHeaderBackgroundColor` in `DatePickerTheme` for M2

```dart
      theme: ThemeData(
        useMaterial3: false,
        datePickerTheme: const DatePickerThemeData(
          rangePickerHeaderBackgroundColor: Colors.red,
        ),
      ),
```

| Before | After |
| --------------- | --------------- |
| <img src="https://github.com/flutter/flutter/assets/48603081/4e85a115-c702-45b2-8f1e-2f3c87c37629" /> | <img src="https://github.com/flutter/flutter/assets/48603081/d002ba0a-6328-4f97-8ba0-dcbb9662bbb3"  /> |
2024-04-26 04:18:24 +00:00
..
2024-04-09 19:35:07 +00:00
2024-04-22 16:49:19 +00:00