[caffe2] plan executor error propagation test with blocking cancellable op (#45319)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45319
## Motivation
* `Cancel` is now added to `OperatorBase` and `NetBase` (https://github.com/pytorch/pytorch/pull/44145)
* We need a test to cover and exhibit that we can cancel stuck net and propagate error with plan executor.
## Summary
* Added `ErrorPlanWithCancellableStuckNet` for plan executor.
* We set a plan with two nets: one stuck net with blocking operator that never returns, and one with error
net with error op that throws, and tested it throw and cancel.
Test Plan:
## Unit Test added
```
buck test caffe2/caffe2:caffe2_test_cpu -- PlanExecutorTest
buck test caffe2/caffe2:caffe2_test_cpu -- PlanExecutorTest --stress-runs 100
```
```
Summary
Pass: 400
ListingSuccess: 2
```
Reviewed By: d4l3k
Differential Revision: D23920548
fbshipit-source-id: feff41f73698bd6ea9b744f920e0fece4ee44438
