Update to data sampler

[dfulu]

Update the library to work with ocf_data_sampler

This is still a work in progress

TODO:

• UK backtest still uses datapipes since it requires concurrent samples. We need a concurrent sampler in data-samples to replace this
• The UK regional dataloader has been updated to data-sampler. Others have not since we have not built data samplers for them
• Possibly more. It's been a while since I looked at this code