add required when generating methods with nnbd named arguments. #3770
Description
If I use quickfix 'create method xxxx' and the method signature is:
final package = await DaoPackage().tryByMember(packageName: packageName);
The resulting generated signature is:
tryByMember({String packageName}) {}
`
The signature should be:
```dart
tryByMember({required String packageName}) {}as nnbd named arguments require the 'required' keyword.