Bug fixes for memory attribution and multiprocessing

What's Changed

Improved functionality and accuracy:

• Fixed Python memory attribution for large requests.
• Fixed an issue with the multiprocessing library.

UI improvements:

• Fixed reporting of the Python fraction of memory allocated.

Compatibility:

• Removed nvidia-ml-py dependency, which was causing a reported issue with Dask (#378).

Full Changelog: v1.5.5...v1.5.6