[DataPipe] Adding examples for MapDataPipes with small fixes for others (#73250)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/73250
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D34400782
Pulled By: NivekT
fbshipit-source-id: 4b8fc83a5a39d9661efbedc764cc68b1714db5c7
(cherry picked from commit 5f376972f0fa5ce10a40b8b083cc00de2ad237fe)
