Deleted file:
* `product_list_dialog_helper.dart`
Impacted files:
* `basic_test.dart`: refactored
* `loading_dialog.dart`: refactored
* `product_dialog_helper.dart`: refactored
* `smooth_alert_dialog.dart`: now constructors for simple and advanced effects
* `user_contribution_view.dart`: now explicitly using the "advanced" dialog
* `user_preferences_profile.dart`: refactored
* `user_preferences_settings.dart`: now explicitly using the "advanced" dialog