Adding DataLoader2 class as future replacement of DataLoader (#63523)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63523
Supports sharding and batching on loader level**
* #63522 Adding IterableAsDataPipe IterDataPipe
usefull for tests and simple cases
Supports sharding and batching on loader level
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D30426527
Pulled By: VitalyFedyunin
fbshipit-source-id: e5905d3364c4880e720dd62fb066f08881c71a6e
