API deprecate positional args in file_download and hf_api (#745)
* API deprecate positional args in file_download and hf_api
* allow positional filters
* add _deprecation.py
* fix imports
* fix import order
* Lysandre's suggestion
* fix test_snapshot_download related issues
* allow more positional args and test fixes
* fix test_hf_api.py
* use f-string
* refine positional args
* let repo_id be positional
* allow positional path_in_repo in delete_file
* more changes
* make another repo_id positional
* fix a few more warnings
* fix tests