Add MetNetPV training script

[jacobbieker]

Pull Request

Description

Adds training script for the new MetNetPV model version

Fixes #

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.
Please also list any relevant details for your test configuration

• Yes

If your changes affect data processing, have you plotted any changes? i.e. have you done a quick sanity check?

• Yes

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings

[jacobbieker]

Going to attempt a few more tests -> 1. Try MetNet that outputs all future timesteps at once 'MetNetSingleShot', 2. Run with just sun positions to see if it can learn the general trends of night time, 3. Run with smaller inputs (64x64) to fit all 96 timesteps in at once. For all of these, also try running with multiple GPUs on donatello, the new torchdata might have fixed some issues