[Windows] Support building PyTorch with ROCm support

[ScottTodd]

Tracking issue, split from the general Windows platform support issue. See also the discussions at #409.

Goals/tasks:

• Get https://github.com/ROCm/TheRock/tree/main/external-builds/pytorch working on Windows
• Land any necessary patches upstream (e.g. in https://github.com/pytorch/pytorch)
• Produce Python wheels, using either an existing HIP SDK / TheRock install found on the system OR "fat wheels" with ROCm bundled using something like https://github.com/ROCm/TheRock/blob/main/external-builds/pytorch/windows_patch_fat_wheel.py
• Enable enough acceleration libraries, both in ROCm and the community (e.g. Triton), for good out of the box performance
• Test PyTorch itself (manually and with automation)
• Test projects that are built on PyTorch (manually and with automation)