Add `torch.cuda.streams.ExternalStream` (#57781)
Summary:
This is required in https://github.com/pytorch/pytorch/pull/57110#issuecomment-828357947
We need to provide means to synchronize on externally allocated streams for dlpack support in python array data api.
cc mruberry rgommers leofang asi1024 kmaehashi
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57781
Reviewed By: mrshenli
Differential Revision: D28326365
Pulled By: ezyang
fbshipit-source-id: b67858c8033949951b49a3d319f649884dfd0a91
