add XPU backend to support torch.save and torch.load (#89679)
# Motivate
We need to add XPU backend to support torch.save and torch.load when parameter _use_new_zipfile_serialization=False.
# Solution
We give a design via wrap data as a tensor:
>1. and use an in-place copy for H2D
>2. directly call a tensor.to() for D2H.
This can help us:
>1. unify the generic code for all backends.
>2. support all the non-CPU device backends.
# Additional Context
No need more UT.
test/test_serialization.py will cover this code change.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89679
Approved by: https://github.com/ezyang
