Related https://github.com/flutter/flutter/issues/131676

## Description

#### Fix default input text style for `DropdownMenu`

![dropdown_input](https://github.com/flutter/flutter/assets/48603081/301f8243-155a-4b8f-84a8-5e6b7bebb3bc)

### Fix default text style for  `MenuAnchor`'s menu items (which `DropdownMenu` uses for menu items)

![dropdown_item](https://github.com/flutter/flutter/assets/48603081/6b5be81a-72fc-4705-a577-074c7a4cad8f)

###  Default  `DropdownMenu` Input text style 

![Screenshot 2023-08-04 at 16 48 28](https://github.com/flutter/flutter/assets/48603081/bcd9da98-e74d-491e-ae64-6268ae0b3893)

### Default `DropdownMenu` menu item text style

![Screenshot 2023-08-04 at 16 50 19](https://github.com/flutter/flutter/assets/48603081/9592ca43-2854-45b5-8648-203ab65d9745)

### Default `MenuAnchor` menu item text style

![Screenshot 2023-08-04 at 14 34 28](https://github.com/flutter/flutter/assets/48603081/e87e1073-05f8-4dc7-a435-d864e9cce6ab)

### Code sample

<details> 
<summary>expand to view the code sample</summary> 

```dart
import 'package:flutter/material.dart';

/// Flutter code sample for [DropdownMenu]s. The first dropdown menu has an outlined border.

void main() => runApp(const DropdownMenuExample());

class DropdownMenuExample extends StatefulWidget {
  const DropdownMenuExample({super.key});

  @override
  State<DropdownMenuExample> createState() => _DropdownMenuExampleState();
}

class _DropdownMenuExampleState extends State<DropdownMenuExample> {
  final TextEditingController colorController = TextEditingController();
  final TextEditingController iconController = TextEditingController();
  ColorLabel? selectedColor;
  IconLabel? selectedIcon;

  @override
  Widget build(BuildContext context) {
    final List<DropdownMenuEntry<ColorLabel>> colorEntries =
        <DropdownMenuEntry<ColorLabel>>[];
    for (final ColorLabel color in ColorLabel.values) {
      colorEntries.add(
        DropdownMenuEntry<ColorLabel>(
            value: color, label: color.label, enabled: color.label != 'Grey'),
      );
    }

    final List<DropdownMenuEntry<IconLabel>> iconEntries =
        <DropdownMenuEntry<IconLabel>>[];
    for (final IconLabel icon in IconLabel.values) {
      iconEntries
          .add(DropdownMenuEntry<IconLabel>(value: icon, label: icon.label));
    }

    return MaterialApp(
      theme: ThemeData(
        useMaterial3: true,
        colorSchemeSeed: Colors.green,
        // textTheme: const TextTheme(
        //   bodyLarge: TextStyle(
        //     fontWeight: FontWeight.bold,
        //     fontStyle: FontStyle.italic,
        //     decoration: TextDecoration.underline,
        //   ),
        // ),
      ),
      home: Scaffold(
        body: SafeArea(
          child: Column(
            children: <Widget>[
              const Text('DropdownMenus'),
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 20),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    DropdownMenu<ColorLabel>(
                      controller: colorController,
                      label: const Text('Color'),
                      dropdownMenuEntries: colorEntries,
                      onSelected: (ColorLabel? color) {
                        setState(() {
                          selectedColor = color;
                        });
                      },
                    ),
                    const SizedBox(width: 20),
                    DropdownMenu<IconLabel>(
                      controller: iconController,
                      enableFilter: true,
                      leadingIcon: const Icon(Icons.search),
                      label: const Text('Icon'),
                      dropdownMenuEntries: iconEntries,
                      inputDecorationTheme: const InputDecorationTheme(
                        filled: true,
                        contentPadding: EdgeInsets.symmetric(vertical: 5.0),
                      ),
                      onSelected: (IconLabel? icon) {
                        setState(() {
                          selectedIcon = icon;
                        });
                      },
                    ),
                  ],
                ),
              ),
              const Text('Plain TextFields'),
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 20),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    SizedBox(
                      width: 150,
                      child: TextField(
                          controller: TextEditingController(text: 'Blue'),
                          decoration: const InputDecoration(
                            suffixIcon: Icon(Icons.arrow_drop_down),
                            labelText: 'Color',
                            border: OutlineInputBorder(),
                          )),
                    ),
                    const SizedBox(width: 20),
                    SizedBox(
                      width: 150,
                      child: TextField(
                          controller: TextEditingController(text: 'Smile'),
                          decoration: const InputDecoration(
                            prefixIcon: Icon(Icons.search),
                            suffixIcon: Icon(Icons.arrow_drop_down),
                            filled: true,
                            labelText: 'Icon',
                          )),
                    ),
                  ],
                ),
              ),
              if (selectedColor != null && selectedIcon != null)
                Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    Text(
                        'You selected a ${selectedColor?.label} ${selectedIcon?.label}'),
                    Padding(
                      padding: const EdgeInsets.symmetric(horizontal: 5),
                      child: Icon(
                        selectedIcon?.icon,
                        color: selectedColor?.color,
                      ),
                    )
                  ],
                )
              else
                const Text('Please select a color and an icon.')
            ],
          ),
        ),
      ),
    );
  }
}

enum ColorLabel {
  blue('Blue', Colors.blue),
  pink('Pink', Colors.pink),
  green('Green', Colors.green),
  yellow('Yellow', Colors.yellow),
  grey('Grey', Colors.grey);

  const ColorLabel(this.label, this.color);
  final String label;
  final Color color;
}

enum IconLabel {
  smile('Smile', Icons.sentiment_satisfied_outlined),
  cloud(
    'Cloud',
    Icons.cloud_outlined,
  ),
  brush('Brush', Icons.brush_outlined),
  heart('Heart', Icons.favorite);

  const IconLabel(this.label, this.icon);
  final String label;
  final IconData icon;
}

``` 
	
</details>