Standardize

[tung-nd]

An effort to clean and standardize the code:

1. Instead of having a rollout function and an upsample function, we now have a unified evaluation function used for evaluating models.
2. Standardize the shape of the prediction to [B, C, H, W]. This is consistent with all metrics and losses.
3. Remove redundant code in forecasting and downscaling Module classes, and make changes to adhere to changes in model components and metrics.

[tung-nd]

@se0ngbin now we also compute w_mse during evaluation, which can be used for early stopping

[jasonjewik]

If you can't get around to doing these, I'll do it myself sometime in the next couple days.

[tung-nd]

Will really appreciate if you can do it :)

[jasonjewik]

Just checked the notebooks. Seems fine to me. Approved for merge.