Adding train, test and predict utility methods

[mikeheddes]

We would like to implement as part of this library the train, test, and predict utility functions like those provided in: https://github.com/rishikanthc/torch-hd/blob/main/torch_hd/utils.py. This issue serves as the discussion thread for how to design theses functions to be simple, and generally applicable for HDC learning applications.

[mikeheddes]

I am closing this because similar functionality can be obtained with the model classes.