[Feature]: Revamp the Transform hyperparameter loading

[hwpang]

Notes
From @davidegraff 's comment from #726

I feel like I'm broadly happy with this PR and there are some minor kinks to work out now. That said, I think there's two main extensions to this PR for the future:

1. revamp the hyperparameter loading. The current implementation works and correctly stores the transforms in their respective modules, but it reintroduces duplicated memory that more efficient module checkpointing #444 attempted to address. In short, by saving the modules themselves as hyperparameters, their respective state dicts are stored twice in the checkpoint file: once with the scaler object itself and and once inside the entire model's state dict. Again, not a big deal considering these are O(24)−O(29), i.e, less than 1 KB each. There are only about five of them in the entire model, so this is practically a non-issue. However, it wouldn't be bad for someone to try and address this to maintain thematic consistency with the rest of the code, but it may be more trouble than it's worth...