Improve default parameter naming for
[Interceptor](https://github.com/cfug/dio/blob/a7a787840b87def9d16c10c009c548ddfcd86337/dio/lib/src/interceptor.dart#L192-L206).

```dart
class Interceptor {
  /// The constructor only helps sub-classes to inherit from.
  /// Do not use it directly.
  const Interceptor();

  /// Called when the request is about to be sent.
  void onRequest(
    RequestOptions options,
    RequestInterceptorHandler handler,
  ) {
    handler.next(options);
  }

  /// Called when the response is about to be resolved.
  void onResponse(
    Response response,
    ResponseInterceptorHandler handler,
  ) {
    handler.next(response);
  }

  /// Called when an exception was occurred during the request.
  void onError(
    DioException err,
    ErrorInterceptorHandler handler,
  ) {
    handler.next(err);
  }
}
```

### New Pull Request Checklist

- [x] I have read the
[Documentation](https://pub.dev/documentation/dio/latest/)
- [x] I have searched for a similar pull request in the
[project](https://github.com/cfug/dio/pulls) and found none
- [x] I have updated this branch with the latest `main` branch to avoid
conflicts (via merge from master or rebase)
- [ ] I have added the required tests to prove the fix/feature I'm
adding
- [ ] I have updated the documentation (if necessary)
- [x] I have run the tests without failures
- [ ] I have updated the `CHANGELOG.md` in the corresponding package

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