Support audio in rows and search
Using this code I can run `to_rows_list` in less than 2sec on 100 wav files of 1.5MB (from 20sec before).
I chose to stop converting to WAV and only send the MP3 file to the user, and to parallelize the audio conversions.

This should enable the viewer on audio datasets for both /rows and /search :)
Though to try this feature on /rows I first enabled it on `arabic_speech_corpus` and will enable it on all datasets if it works fine

Note: this can probably be improved later, e.g. by avoiding unnecessary conversions

related to https://github.com/huggingface/datasets-server/issues/1255
Support audio in rows and search: Using this code I can run `to_rows_list` in less than 2sec on 100 wav files of 1.5MB (from 20sec before).
I chose to stop converting to WAV and only send the MP3 file to the user, and to parallelize the audio conversions.

This should enable the viewer on audio datasets for both /rows and /search :)
Though to try this feature on /rows I first enabled it on `arabic_speech_corpus` and will enable it on all datasets if it works fine

Note: this can probably be improved later, e.g. by avoiding unnecessary conversions

related to https://github.com/huggingface/datasets-server/issues/1255