Fix NavigationRail's indicator inkwell doesn't support transparent color. (#136359)
fixes [NavigationRail can't have a transparent Hover color because there is always opacity set](https://github.com/flutter/flutter/issues/135866)
### 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(
colorScheme: ColorScheme.fromSeed(seedColor: Colors.green).copyWith(
primary: Colors.transparent,
),
),
home: const Example(),
);
}
}
class Example extends StatefulWidget {
const Example({Key? key}) : super(key: key);
@override
State<StatefulWidget> createState() => _ExampleState();
}
class _ExampleState extends State<Example> {
int _selectedIndex = 0;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('NavigationRail Example'),
),
body: Row(
children: <Widget>[
NavigationRail(
selectedIndex: _selectedIndex,
onDestinationSelected: (int index) {
setState(() {
_selectedIndex = index;
});
},
labelType: NavigationRailLabelType.all,
destinations: const <NavigationRailDestination>[
NavigationRailDestination(
icon: Icon(Icons.favorite_border),
selectedIcon: Icon(Icons.favorite),
label: Text('First'),
),
NavigationRailDestination(
icon: Icon(Icons.bookmark_border),
selectedIcon: Icon(Icons.book),
label: Text('Second'),
),
NavigationRailDestination(
icon: Icon(Icons.star_border),
selectedIcon: Icon(Icons.star),
label: Text('Third'),
),
],
),
const VerticalDivider(thickness: 1, width: 1),
Expanded(
child: Center(
child: Text('Selected Index: $_selectedIndex'),
),
)
],
),
);
}
}
```
</details>
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