Support streaming FLEURS dataset
Yes, you just have to use `dl_manager.iter_archive` instead of `dl_manager.download_and_extract`.

That's because `download_and_extract` doesn't support TAR archives in streaming mode. Tried to make it streamable, but I don't think it's really possible. @lhoestq @polinaeterna maybe you guys can check: 
https://huggingface.co/datasets/google/fleurs/commit/dcf80160cd77977490a8d32b370c027107f2407b 

real quick. 

I think the problem is that we cannot ensure that the metadata file is found before the audio. Or is this possible somehow @lhoestq ?  @patrickvonplaten I think the metadata file should be found first because the audio files are contained in a folder next to the metadata files (just as in common voice), so the metadata files should be "on top of the list"   as they are closer to the root in the directories hierarchy  @patrickvonplaten but apparently it doesn't... I don't really know why. Yeah! Any ideas what could be the reason here? cc @lhoestq ? The order of the files is determined when the TAR archive is created, depending on the commands the creator ran.
If the metadata file is not at the beginning of the file, that makes streaming completely inefficient. In this case the TAR archive needs to be recreated in an appropriate order. Actually we could maybe just host the metadata file ourselves and then stream the audio data only. Don't think that this would be a problem for the FLEURS authors (I can ask them :-))  I made a PR to their repo to support streaming (by uploading the metadata file to the Hub). See:
- https://huggingface.co/datasets/google/fleurs/discussions/4 I'm closing this issue as the PR above has been merged.
## Dataset viewer issue for '*name of the dataset*'

https://huggingface.co/datasets/google/fleurs

```
Status code:   400
Exception:     NotImplementedError
Message:       Extraction protocol for TAR archives like 'https://storage.googleapis.com/xtreme_translations/FLEURS/af_za.tar.gz' is not implemented in streaming mode. Please use `dl_manager.iter_archive` instead.
```

Am I the one who added this dataset ? Yes

Can I fix this somehow in the script? @lhoestq @severo 
