Adding printouts for uncounted MACs in modules

[danielamassiceti]

This PR:

• adds in functionality which checks what modules have their MACs counted, and prints out a list of those that require a custom_ops function to be written.
• updates the checkpoint in the Challenge notebook to vit_b_32_clip.
• updates the way single- and multi-step-learner.py print out the final scores at the end of a run