pytorch

56d74f7b - [LT] Move the DDP fallback prototype into a ProcessGroup Python extension (#74709)

[LT] Move the DDP fallback prototype into a ProcessGroup Python extension (#74709) Summary: This commit moves the DDP fallback prototype into a ProcessGroup Python extension such that it's less invasive to torch.distributed. And hopefully this is ready to upstream. Test Plan: LTC_TS_CUDA=1 python lazy_tensor_core/test/ddp/ddp.py