Add cancelButtonStyle & confirmButtonStyle to the DatePickerThemeData (#132847)
fixes [Unable to adjust the color for "Cancel" and "Ok" button in datePicker dialog](https://github.com/flutter/flutter/issues/127739)
### 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: true,
datePickerTheme: DatePickerThemeData(
cancelButtonStyle: TextButton.styleFrom(
shape: const RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(16)),
side: BorderSide(color: Colors.red),
),
backgroundColor: Colors.white,
foregroundColor: Colors.red,
elevation: 3,
shadowColor: Colors.red,
),
confirmButtonStyle: TextButton.styleFrom(
shape: const RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(16)),
),
backgroundColor: Colors.green[700],
foregroundColor: Colors.white,
elevation: 3,
shadowColor: Colors.green[700],
),
),
),
home: const Example(),
);
}
}
class Example extends StatelessWidget {
const Example({super.key});
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: DatePickerDialog(
initialDate: DateTime.now(),
firstDate: DateTime(2020),
lastDate: DateTime(2030),
),
),
);
}
}
```
</details>
### Before
Not possible to customize action buttons from the `DatePickerThemeData`.
### After
1e770c3808