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

examples/pytorch/token-classification/run_ner_no_trainer.py

@@ -48,7 +48,7 @@ from transformers import (
     get_scheduler,
     set_seed,
 )
-from transformers.file_utils import get_full_repo_name
+from transformers.utils import get_full_repo_name
 from transformers.utils.versions import require_version