Fix typo in new -config-file option

The new -config-file option introduced by 9e1f4f13 was accidentally
referenced as args.config_path on the python side. This patch renames
args.config_path to args.config_file.

To avoid confusion with python file objects, the input argument for
get_tidy_invocation has been renamed from config_path to
config_file_path.

See GitHub issue #54728 for a discussion.