[DataPipe] Renaming FileLoader to FileOpener with deprecation warning for FileLoader (#70367)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70367
This PR renames the `FileLoaderIterDataPipe` to `FileOpenerIterDataPipe`. For the sake of not breaking many CI tests immediately, it still preserves `FileLoader` as an alias. This will allow downstream libraries/users to migrate their use cases before we fully remove all references to `FileLoader` from PyTorch.
Fixes https://github.com/pytorch/data/issues/103. More detailed discussion about this decision is also in the linked issue.
cc VitalyFedyunin ejguan NivekT pmeier Nayef211
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D33301648
Pulled By: NivekT
fbshipit-source-id: 59278dcd44e372df0ba2001a4eecbf9792580d0b
