Reorganize file utils (#16264)

* Split file_utils in several submodules

* Fixes

* Add back more objects

* More fixes

* Who exactly decided to import that from there?

* Second suggestion to code with code review

* Revert wront move

* Fix imports

* Adapt all imports

* Adapt all imports everywhere

* Revert this import, will fix in a separate commit

src/transformers/testing_utils.py

@@ -30,7 +30,8 @@ from unittest import mock
 from transformers import logging as transformers_logging
 
 from .deepspeed import is_deepspeed_available
-from .file_utils import (
+from .integrations import is_optuna_available, is_ray_available, is_sigopt_available, is_wandb_available
+from .utils import (
     is_detectron2_available,
     is_faiss_available,
     is_flax_available,
@@ -60,7 +61,6 @@ from .file_utils import (
     is_torchaudio_available,
     is_vision_available,
 )
-from .integrations import is_optuna_available, is_ray_available, is_sigopt_available, is_wandb_available
 
 
 SMALL_MODEL_IDENTIFIER = "julien-c/bert-xsmall-dummy"