FIX batchkey enum bug

[AUdaltsova]

Pull Request

On previous merge I added new batchkeys in the middle of the class, which is enumerated, so it bumps all the keys after the new ones 4 down when unpacking premade batches, leading to errors. This PR puts the keys at the bottom, where they should've been in the first place

I think this only affects batches stored as tensors, as .netcdf batches have labels that get converted to BatchKeys.

How Has This Been Tested?

Ran the full battery of PVNet tests locally, for two versions of PVNet: current and with this fix.

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

[Sukh-P]

Nice catch!