Gracefully handle failure of DataPtr extraction in CUDAFuture (#56511)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56511
CUDAFuture needs to inspect the value in order to extract DataPtrs. Sometimes it's unable to do so. So far we've handled this by raising an error when `markCompleted` is called. In this PR I'm proposing a change, which makes `markCompleted` return successfully, but instead causes the Future to be set to an error if the DataPtr extraction fails.
The advantages I see are that user code calling `markCompleted` didn't expect it to throw, and thus wasn't catching and handle that error. Which in the best case could lead to a crash, and in the worst case could lead to the Future remaining incomplete, thus not unblocking any client waiting on it. With this change those clients would be woken up and would see the error.
ghstack-source-id: 127035772
Test Plan: Unit tests
Reviewed By: mrshenli
Differential Revision: D27861070
fbshipit-source-id: 4bb6100a488ab35fbe3c2bc3ac6f98d166c60a0b
