Update `datasets` to 2.16.1
...and hfh to 0.20.1

This enables:

- Webdataset support for the Dataset Viewer
- Faster data files resolution, which makes listing configs, splits and generating parquet export faster
- Less pressure on the HF back-end (less /tree calls on the Hub, and they no longer use expand=true)

In addition to the update:

- I removed the #2001 hot-fix and replaced it with a proper use of `trust_remote_code`
- I set `HF_DATASETS_TRUST_REMOTE_CODE=0` by default
- I set `datasets.config.USE_PARQUET_EXPORT = False` since we don't need to query parquer exports when loading datasets (this is just to avoid unnecessary calls)

Fix https://github.com/huggingface/datasets-server/issues/2229

TODO:

- [x] fix tests

TODO after the update + deploy:

- [x] re-generate webdatasets on the hub, e.g.
  - [x] https://huggingface.co/datasets/timm/imagenet-12k-wds
  - [x] https://huggingface.co/datasets/pixparse/cc12m-wds
  - [x] https://huggingface.co/datasets/pixparse/cc3m-wds
Update `datasets` to 2.16.1: ...and hfh to 0.20.1

This enables:

- Webdataset support for the Dataset Viewer
- Faster data files resolution, which makes listing configs, splits and generating parquet export faster
- Less pressure on the HF back-end (less /tree calls on the Hub, and they no longer use expand=true)

In addition to the update:

- I removed the #2001 hot-fix and replaced it with a proper use of `trust_remote_code`
- I set `HF_DATASETS_TRUST_REMOTE_CODE=0` by default
- I set `datasets.config.USE_PARQUET_EXPORT = False` since we don't need to query parquer exports when loading datasets (this is just to avoid unnecessary calls)

Fix https://github.com/huggingface/datasets-server/issues/2229

TODO:

- [x] fix tests

TODO after the update + deploy:

- [x] re-generate webdatasets on the hub, e.g.
  - [x] https://huggingface.co/datasets/timm/imagenet-12k-wds
  - [x] https://huggingface.co/datasets/pixparse/cc12m-wds
  - [x] https://huggingface.co/datasets/pixparse/cc3m-wds