In order to support butler I/O for HSC's bespoke stray-light correction files, we should:
- Add an abstract base class for camera-generic stray light correction information to ip_isr, and make the implementation in obs_subaru inherit from it.
- Add a StorageClass to daf_butler for the abstract base class.
- Add a formatter to obs_subaru for the concrete HSC class.
- Add code and possibly a script to ingest the stray light data into a Gen3 repository.