Parquet worker
<strike>Blocked by https://github.com/huggingface/huggingface_hub/issues/1165 (create the `refs/convert/parquet` ref)</strike>.

<strike>We'll maybe wait for hfh 0.11 instead of depending on the main branch</strike>

hfh 0.11.0 has been released, and we upgraded it in datasets-server: https://github.com/huggingface/datasets-server/pull/643

Limitations:
- gated datasets with "extra fields" are not supported

Wait for https://github.com/huggingface/datasets-server/pull/650, then rebase only to add the parquet implementation.
Parquet worker: <strike>Blocked by https://github.com/huggingface/huggingface_hub/issues/1165 (create the `refs/convert/parquet` ref)</strike>.

<strike>We'll maybe wait for hfh 0.11 instead of depending on the main branch</strike>

hfh 0.11.0 has been released, and we upgraded it in datasets-server: https://github.com/huggingface/datasets-server/pull/643

Limitations:
- gated datasets with "extra fields" are not supported

Wait for https://github.com/huggingface/datasets-server/pull/650, then rebase only to add the parquet implementation.