randperm: add torch check to ensure generator device = tensor device (#47022)
Summary:
**BC-breaking Note:**
This PR disallows passing in a generator of a different device than the tensor being created during `randperm` execution. For example, the following code which used to work no longer works.
```
> torch.randperm(3, device='cuda', generator=torch.Generator(device='cpu'))
tensor([0, 1, 2], device='cuda:0')
```
It now errors:
```
> torch.randperm(3, device='cuda', generator=torch.Generator(device='cpu'))
RuntimeError: Expected a 'cuda:0' generator device but found 'cpu'
```
**PR Summary:**
Fixes https://github.com/pytorch/pytorch/issues/44714
Also added + ran tests to ensure this functionality.
Disclaimer: More work needs to be done with regards to small cuda tensors when a generator is specified, look at the issue thread for more details.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47022
Reviewed By: samestep
Differential Revision: D24608237
Pulled By: janeyx99
fbshipit-source-id: b83c47219c7816d93f938f7ce86dc8857513961b
