[WIP] Add Jukebox model 
This is a draft pull request. 

# What does this PR do?
This PR will progressively add the [Jukebox](https://openai.com/blog/jukebox/) model to the hub.
It is linked to [#16870](https://github.com/huggingface/transformers/issues/16870). 

# Currently planned steps (WIP)

- [x]  Create template files with `transformeres-cli add-new-model-like`
- [x] `src/transformers/tokenization_jukebox.py`
- [x]  `src/transformers/test_tokenization_jukebox.py`
- [x]  `src/transformers/configuration_jukebox.py`
- [x]  `src/transformers/modeling_jukebox.py`
- [ ]  `src/transformers/configuration_jukebox.py`
- [ ]  `docs/source/model_doc/jukebox.rst`
- [ ] `src/transformers/tokenization_jukebox_fast.py` (will most probably use WordLevel tokenizer). Also requires to implement a converter function `class JukeboxConverter(Converter):`



Tokenizer and corresponding test should be done. Lacking some detailed description and also probably something about the arguments in the init that are not data but I don't remember if I should create setters (@patrickvonplaten would love to have your review)<|||||>Cool nice to see much progress here! 

Feel free to also add a file that shows how you compare OpenAI's original to the current (HF) implementation<|||||>What happened to the git commit history here?<|||||>I rebased instead of merging 🤕 Will create a new PR to replace that one <|||||>See followup in #17826 