Add ImageSequenceReference support to File bunder adapters (OTIO[d|z])

[ssteinbach]

Currently the file bundle adapters only support external references: https://github.com/AcademySoftwareFoundation/OpenTimelineIO/blob/6cd4161aa3adfbca6544798158a8b5f006235f6b/src/py-opentimelineio/opentimelineio/adapters/file_bundle_utils.py#L113

ImageSequenceReferences that can resolve to files on disk should also be supportable by MediaReferences.