Make using safetensors files automated. (#27571)

* [WIP] Make using safetensors files automated.

If `use_safetensors=True` is used, and it doesn't exist:

- Don't crash just yet
- Lookup for an open PR containing it.
- If yes, use that instead
- If not, touch the space to convert, wait for conversion to be finished
  and the PR to be opened
- Use that new PR
- Profit.

* Remove the token.

* [Auto Safetensors] Websocket -> SSE (#27656)

* Websocket -> SSE

* Support sharded + tests +cleanup

a

* env var

* Apply suggestions from code review

* Thanks Simon

* Thanks Wauplin

Co-authored-by: Wauplin <lucainp@gmail.com>

* Cleanup

* Update tests

* Tests should pass

* Apply to other tests

* Extend extension

* relax requirement on latest hfh

* Revert

* Correct private handling & debug statements

* Skip gated repos as of now

* Address review comments

Co-authored-by: ArthurZucker <arthur.zucker@gmail.com>

---------

Co-authored-by: Lysandre Debut <hi@lysand.re>
Co-authored-by: Lysandre <lysandre@huggingface.co>
Co-authored-by: Wauplin <lucainp@gmail.com>
Co-authored-by: Lysandre <lysandre.debut@reseau.eseo.fr>
Co-authored-by: ArthurZucker <arthur.zucker@gmail.com>

utils/check_inits.py

@@ -330,6 +330,7 @@ IGNORE_SUBMODULES = [
     "modeling_flax_pytorch_utils",
     "models.esm.openfold_utils",
     "modeling_attn_mask_utils",
+    "safetensors_conversion",
 ]