[DataLoader] Rename Callable to Map IterDataPipe (#51879)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/51879
Test Plan: Imported from OSS
Reviewed By: VitalyFedyunin
Differential Revision: D26314775
Pulled By: ejguan
fbshipit-source-id: ee77909eae97092155ed6a6c794540e68a04d754
