[reland] Create torch.distributed._shard package. (#72141)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72141
We have many sharding components currently:
torch.distributed._sharded_tensor, torch.distributed._sharding_spec,
torch.distributed._sharded_optimizer and more coming.
As a result, organizing all of this under the `torch.distributed._shard`
package. For BC reasons, I'm still keeping the old packages and have them just
reference the new package.
ghstack-source-id: 148150861
ghstack-source-id: 148150861
Test Plan: waitforbuildbot
Reviewed By: fduwjj
Differential Revision: D33904585
fbshipit-source-id: 057e847eb7521b536a3ee4e0f94871aacc752062
(cherry picked from commit 29a70dd7afde6083bab942081020a13278f38e52)
