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/flax/summarization/run_summarization_flax.py

@@ -54,7 +54,7 @@ from transformers import (
     HfArgumentParser,
     is_tensorboard_available,
 )
-from transformers.file_utils import get_full_repo_name, is_offline_mode
+from transformers.utils import get_full_repo_name, is_offline_mode
 
 
 logger = logging.getLogger(__name__)