Allow `_JigsawToxicityDatasetBuilder` to load bias labels.
Allow `_JigsawToxicityDatasetBuilder` to load bias labels.

This allows user to store a dictionary {'id': List[str]} of biased examples to `data_dir`. So model can generate binary labels for whether an example has a bias score.

PiperOrigin-RevId: 444460641

google/uncertainty-baselines