Summary:
Currently, arrow iterator can only read arrow files. However, the pyarrow library can read
other formats, including jsonlines. This allows the same ArrowIterator to read from jsonlines,
so we can read from the original source data, and simply omit the entropy column when doing so
Test Plan:
Run train script until dataloader starts
* allow loading of the entropy model directly
* remove unused argument
* remove spammy warning
* allow patch_batch_size to be adjusted in the forward() method
* revert to original patcher style, fix warning
* allow grads when calculating entropies
* fix grad flow
* return preds from calculate_entropies()
* remove legacy arg
* fix an error with monotonicity and small sequence lengths
* ensure patcher is serializable
* revert patcher to original
* remove unused import
