Add manifold support for fairseq file_io
Add manifold support for fairseq file_io

Summary: Recently fairseq file_io migrated to iopath in D27109864 (https://github.com/pytorch/fairseq/commit/fc90910314ce02fe168bdbe127e08a14e944a6fd). New IOPathManager doesn't have manifold support by default. Add manifold handler to fix the issue.

Reviewed By: myleott

Differential Revision: D27809504

fbshipit-source-id: 5cbf4440ed734132f865096c45cd3e47ccb6142d

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq