[torch/deploy] add torch.distributed to build (#63918)

[torch/deploy] add torch.distributed to build (#63918)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63918

Previously we were building with `USE_DISTRIBUTED` off, because c10d was built as a separately library for historical reasons. Since then, lw has merged the c10d build into libtorch, so this is fairly easy to turn on.

Differential Revision:
D30492442

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D30492442
D30492442

Test Plan: added a unit test

Reviewed By: wconstab

Pulled By: suo

fbshipit-source-id: 843b8fcf349a72a7f6fcbd1fcc8961268690fb8c