[DataPipe] removing filter's inheritance from map (#64404)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64404
This PR remove `filter`'s inheritance from `map`. This allows `filter` to not have a `__len__` function and that behavior is what we would like.
cc VitalyFedyunin ejguan
Test Plan: Imported from OSS
Reviewed By: gchanan
Differential Revision: D30713120
Pulled By: NivekT
fbshipit-source-id: 4d5d07555297ee2bd4b49842c0d26cdc00638f6c
