[DataLoader] Move BufferedShuffle from Dataset to DataPipe (#52141)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52141
Remove BufferShuffleDataSet, as it's not being used anywhere within PyTorch (no usage on Github based on a search) and it's not included in the release of PyTorch 1.7.1.
Test Plan: Imported from OSS
Reviewed By: H-Huang
Differential Revision: D26710940
Pulled By: ejguan
fbshipit-source-id: 90023b4bfb105d6aa392753082100f9181ecebd0
