Remove redundant files and codes from rnd folder

[alirezakazemipour]

Summary of changes:

• Change Common and Brain folders to python packages.
• Remove play.py as that was not needed.
• Remove Montezuma's Revenge environment wrappers as they were not needed.
• Replace clip_grad_norm_ method with the official torch.clip_grad_norm_.

[danijar]

Thanks for cleaning up! I'll keep the current version because reproduces the results in the paper and refactoring can sometimes introduce unexpected changes.

[alirezakazemipour]

Definitely!
As what you consider to be appropriate.
It's been a pleasure anyway. 🙏