Fix torch.cuda.check_error type errors (#41330)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41330
`torch.cuda.check_error` is annotated as taking an `int` as argument but when running `torch.cuda.check_error(34)` one would get:
```
TypeError: cudaGetErrorString(): incompatible function arguments. The following argument types are supported:
1. (arg0: torch._C._cudart.cudaError) -> str
Invoked with: 34
```
Even if one explicitly casted the argument, running `torch.cuda.check_error(torch._C._cudart.cudaError(34))` would give:
```
AttributeError: 'str' object has no attribute 'decode'
```
This PR fixes both issues (thus allowing `check_error` to be called with a un-casted int) and adds a test.
ghstack-source-id: 107628709
Test Plan: Unit tests
Reviewed By: ezyang
Differential Revision: D22500549
fbshipit-source-id: 9170c1e466dd554d471e928b26eb472a712da9e1
