Enable safetensors conversion from PyTorch to other frameworks without the torch requirement (#27599)

* Initial commit

* Requirements & tests

* Tests

* Tests

* Rogue import

* Rogue torch import

* Cleanup

* Apply suggestions from code review

Co-authored-by: Nicolas Patry <patry.nicolas@protonmail.com>

* bfloat16 management

* Sanchit's comments

* Import shield

* apply suggestions from code review

* correct bf16

* rebase

---------

Co-authored-by: Nicolas Patry <patry.nicolas@protonmail.com>
Co-authored-by: sanchit-gandhi <sanchit@huggingface.co>

setup.py

@@ -158,7 +158,7 @@ _deps = [
     "ruff==0.1.5",
     "sacrebleu>=1.4.12,<2.0.0",
     "sacremoses",
-    "safetensors>=0.3.1",
+    "safetensors>=0.4.1",
     "sagemaker>=2.31.0",
     "scikit-learn",
     "sentencepiece>=0.1.91,!=0.1.92",