Improve help message response for CLI

This merge request moves import of large modules into the main functions of the CLI scripts after input arguments have been parsed. This is to avoid having to wait until a large module is loaded in order to print a help message. This does not affect the runtime of the commands themselves.

Additionally, the hive conversion logic has been moved into its own script. Group determination for hive conversion has also been moved from the CLI script into this new ./policy/hive.py file.

src/rc_gpfs/cli/convert_to_parquet.py

@@ -77,7 +77,7 @@ def submit_batch(**kwargs):
 def convert_to_parquet() -> None:
     args = parse_args()
 
-    from ..policy import convert
+    from ..policy.convert import convert
 
     if args['output_dir'] is None:
         args['output_dir'] = args['input'].parent.joinpath('parquet')