Add Intel PyTorch extension

[do-jason]

This will add Intel(R) Extension for PyTorch which is for Intel(R) GPU support.
This needs Intel patched PyTorch and extension and one can refer https://intel.github.io/intel-extension-for-pytorch/index.html#installation?platform=gpu&version=v2.1.10%2Bxpu page for installation.

This contains the below changes.

• "import intel_extension_for_pytorch as ipex" is needed for Intel GPU and it is optional in Python code to make it work on platform which does not have this package installed.
• torch.xpu is replacement for torch.cuda and this is explicitly used when necessary.
• topaz/cuda.py is replaced by topaz/gpu.py file which is more generic.
• Most use_cuda=True function argument is replaced by device='cpu'.
• torch.*.cuda() is replaced by torch.*.to(device) where device could be 'cpu'|'cuda'|'xpu'.
• There is limitation in using torch.nn.Parallel on Intel GPU.
• ipex.optimize() is additional optimization on Intel GPU. This is added and commented out since not all configuration is supported as of now. This is for future usage.