Cache embeddings transformations individual from other preprocessing

[raphaelschwinger]

This PR:

• reverts embeddings_datamodule changes concerning disk_save_path and saving to disk
• first creates embeddings and then k_samples
• adds property embeddings_save_path to embeddings_datamodule
• saves embedding transformation to disk and load it again
  • dataset, emeddings_model_name, average, sample_rate and max_length have to fit to use saved cache, otherwise emeddings get computed again

TODO

- [ ] check caching with fingerprint from HF.dataset

[raphaelschwinger]

I checked if we could also use Hugging Faces caching feature, but I did not find a way to load the cache automatically. So I decided to stay with the manual caching of the embeddings.

[XgamerTV]

Looks good the only thing is that _save_dataset_to_disk() shouldn't be called in prepare_data as it creates a second file then. If a file already exists only k_samples is needed as far as I can tell but all other methods (_load_data, _preprocess_data, _create_splits, _save_dataset_to_disk) could be skipped. So maybe we should do an if in prepare_data if the file exists and then just call k_samples 🤔

[raphaelschwinger]

@XgamerTV I could not fix the problem described at #10. I moved the cache retrieving to the prepare_dataset function as you suggested.