Support for MPS backend

[Tianyuan-Zhang]

The current version doesn't support for the MPS backend which is available in PyTorch.
Is is possible to add support for MPS backend?
I tried to manually move the tensors and predictive models to MPS device, but got errors when calculating the loss functions.

[LucasBoTang]

Hi Tianyuan,

PyEPO hasn't been tested on the MPS backend. Generally, the device should not affect the calculation of loss functions, but it would help if you could provide the specific error messages you're encountering so I can examine the issue more closely.

If you're comfortable sharing your code, I can also try to test it. However, I don't currently have access to a macOS system currently.

[Tianyuan-Zhang]

mps_bug.zip
I've attached two Jupyter notebooks that show the error.
The first one, I didn't move the tensors to the MPS device, which caused an error when calculating the regret.
The second one, I moved the tensors to the MPS device, but still got an error when calculating the regret.