FR: Support 7zip extraction

[rhofour]

Is your feature request related to a problem? Please describe.
Some datasets (such as YAGO-3: https://yago-knowledge.org/downloads/yago-3) provide their data in 7-Zip archives. Currently TFDS cannot handle this.

Describe the solution you'd like
7-zip should be supported. It's free and open-source (GNU LGPL) so I don't believe there should be any issues including it.

Describe alternatives you've considered
I'm currently unsure if there are any alternatives as the data is not available in another format and I don't have the resources to rehost it.

[Conchylicultor]

This would be nice, unfortunately, there is no 7z support in the python standard library. We could try a third party module, but not sure about those.

Unfortunately , the best solution currently is for the user to manually extract the data and use dl_manager.manual_dir: https://www.tensorflow.org/datasets/add_dataset#manual_download_and_extraction

[Conchylicultor]

Or alternatively, you could try to use path = dl_manager.download('....7z') and use one of the third party module in your dataset _split_generators to read the data.