Add support for fitting estimators on dask bags
The estimators that can handle dask bags should set
the bob_fit_supports_dask_bag as True.
This commit also includes
- Adds a new tag:
bob_fit_supports_dask_bag - Adds a new tag:
bob_checkpoint_featuresfor when you want to always avoid checkpointing features for a specific estimator. - Expose dask_tags, get_bob_tags in the main API
- The SampleWrapper was modified to support
bob_fit_supports_dask_bag - The CheckpointWrapper now loads estimators without losing references correctly.