[DataLoader2] Adding Messages, Protocols, Loop wrappers (#63882)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/63882
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D30627452
Pulled By: VitalyFedyunin
fbshipit-source-id: 561ea2df07f3572e04401171946154024126387b
