Validate config name and data_files in packaged modules
Validate the config attributes `name` and `data_files` in packaged modules by making the derived classes call their parent `__post_init__` method.

Note that their parent `BuilderConfig` validates its attributes `name` and `data_files` in its `__post_init__` method: https://github.com/huggingface/datasets/blob/60d21efbc01e15d0b596ac1072750cbecd91548a/src/datasets/builder.py#L128-L137

This PR makes the derived config classes call their parent `__post_init__` method to validate their `name` and `data_files` attributes.