[caffe2] adds hypothesis test for queue ops cancel (#45178)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45178
## Motivation
* To be able to make C2 ops cancellable so we can safely exit.
* Some C2 operators are now blocking thus being non-cancellable. If an error
occurs we need to be able to safely stop all net execution so we can throw
the exception to the caller.
## Summary
* Adds a hypothesis test for queue ops cancellation.
Test Plan:
## Unit test added to verify that queue ops propagate errors
```
buck test caffe2/caffe2/python:hypothesis_test
buck test caffe2/caffe2/python:hypothesis_test -- test_safe_dequeue_blob__raises_exception_when_hang --stress-runs 1000
```
```
Summary
Pass: 1000
ListingSuccess: 1
```
Reviewed By: d4l3k
Differential Revision: D23847576
fbshipit-source-id: 2fc351e1ee13ea8b32d976216d2d01dfb6fcc1ad
