[FormBuilderDateTimePicker]: Can't open the picker dialog dynamically anymore

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Package/Plugin version

10.0.0

### Platforms

- [x] Android
- [x] iOS
- [x] Linux
- [x] MacOS
- [x] Web
- [x] Windows

### Flutter doctor

Flutter doctor

```bash
[✓] Flutter (Channel stable, 3.29.0, on macOS 13.7.2 22H313 darwin-x64, locale es-419) [1,442ms]
• Flutter version 3.29.0 on channel stable at /Users/gero/fvm/versions/3.29.0
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 35c388afb5 (4 weeks ago), 2025-02-10 12:48:41 -0800
• Engine revision f73bfc4522
• Dart version 3.7.0
• DevTools version 2.42.2

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0) [5.7s]
• Android SDK at /Users/gero/Library/Android/sdk
• Platform android-34, build-tools 34.0.0
• Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
This is the JDK bundled with the latest Android Studio installation on this machine.
To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
• Java version OpenJDK Runtime Environment (build 21.0.3+-79915915-b509.11)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 15.2) [7.1s]
• Xcode at /Applications/Xcode.app/Contents/Developer
• Build 15C500b
• CocoaPods version 1.16.2

[✓] Chrome - develop for the web [46ms]
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2024.2) [45ms]
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build 21.0.3+-79915915-b509.11)

[✓] Android Studio (version 2024.2) [41ms]
• Android Studio at /Volumes/Latest/Applications/Android Studio.app/Contents
• Flutter plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build 21.0.3+-79915915-b509.11)

[✓] VS Code (version 1.96.4) [40ms]
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension can be installed from:
🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (2 available) [9.4s]
• macOS (desktop) • macos • darwin-x64 • macOS 13.7.2 22H313 darwin-x64
• Chrome (web) • chrome • web-javascript • Google Chrome 133.0.6943.143

[✓] Network resources [655ms]
• All expected network resources are available.

• No issues found!
```

### Minimal code example

Code sample

```dart
class PickerBug extends StatefulWidget {
const PickerBug({super.key});

@override
State createState() => _PickerBugState();
}

class _PickerBugState extends State {
final formKey = GlobalKey();
final controller = TextEditingController();
final focusNode = FocusNode();

@override
Widget build(BuildContext context) {
return Scaffold(
body: Padding(
padding: const EdgeInsets.all(20.0),
child: FormBuilder(
key: formKey,
child: Column(
children: [
FormBuilderDateTimePicker(
name: 'dateTime',
controller: controller,
focusNode: focusNode,
barrierDismissible: false,
autovalidateMode: AutovalidateMode.onUserInteraction,
timePickerInitialEntryMode: TimePickerEntryMode.input,
decoration: const InputDecoration(
border: OutlineInputBorder(),
label: Text('DateTime'),
),
)
],
),
),
),
bottomSheet: Padding(
padding: const EdgeInsets.all(20.0),
child: ElevatedButton(
onPressed: () => focusNode.requestFocus(),
child: Text('Request Focus'),
),
),
);
}
}
```

### Current Behavior

Text field is focused, but picker dialog won't open.

### Expected Behavior

In the previous version it was opening the picker dialog.

### Steps To Reproduce

1. Run the sample code.
2. Click the "Request Focus" button.

### Aditional information

I was using `focusNode.requestFocus()` to open the picker dialog dynamically. Is there a new way of doing this in the latest version?