[DataLoader] Rename transform DataPipe to legacy_transform (#60670)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/60670
Test Plan: Imported from OSS
Reviewed By: mruberry
Differential Revision: D29461081
Pulled By: VitalyFedyunin
fbshipit-source-id: 57f53a91db9032a6126e86243ddea9149c473060
