Add DataColumn.headingRowAlignment for DataTable (#144006)
fixes [[`DataTable`] Unable to center the label of a DataColumn without side effects](https://github.com/flutter/flutter/issues/143340)
### 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,
home: MaterialApp(
home: Material(
child: DataTable(
columns: <DataColumn>[
DataColumn(
headingRowAlignment: MainAxisAlignment.center,
onSort: (int columnIndex, bool ascending) {},
label: const Text('Header'),
),
],
sortColumnIndex: 0,
rows: const <DataRow>[
DataRow(
cells: <DataCell>[
DataCell(Center(child: Text('Data'))),
],
),
],
),
),
),
);
}
}
```
</details>
### Center `DataColumn.mainAxisAlignment` without sort arrow
### Center `DataColumn.mainAxisAlignment` with sort arrow
40dda2b4bb