support Ascend NPU backend

[MaskerPRC]

Purpose: Support 3rd-party backend.

Ussage:

"torch.cuda" should be replaced by "device_module"
".cuda()" should be replaced by ".to(device=device_type)"

[MaskerPRC]

@garrett4wade Does there currently exist a plan to support non-GPU platforms? If there is an opportunity, would you be willing to accept support for abstract device PR?

[garrett4wade]

Hi, we indeed have a plan to support devices other than NV GPU. Such a PR will be great!

FYI In our code we use torch.cuda for some GPU-related logging. The device type of computation has been written to realhf.base.constants.current_device().

[MaskerPRC]

Thank you very much, then I am ready to start coding😀