Update PVNet for datasampler

[Sukh-P]

Pull Request

Description

This PR includes:

• Updates PVNet to use the new batch format that ocf-data-sampler produces
• Updates some of the model modules (such as site encoder) to work with samples from the sites data pipeline.
• Some test data has been updated as well to reflect the new batch format

Some updates have not been made in this PR and may be better suited to a separate PR to separate concerns and reduce PR size:

• Using the new SampleKeys rather than strings in places (TBD whether that is what we want)
• Updating some of the network modules to the new batch format that aren't used as often (e.g one of the site encoders)
• Naming consistency, use pv_encoder in some places, I have left this in for now because there are some tests which rely on this (would need to update some HF files to get some from_pretrained tests to work)

How Has This Been Tested?

Getting tests to pass & running training on some premade site samples.

[dfulu]

Looks really good. Thanks for your thoroughness in these changes. I've just got a few questions and comments on here

[dfulu]

Looks great @Sukh-P. Can we make it a squash merge? We haven't in the past in this repo but I think it is much cleaner