Revert "Increased compile time max GPUs to 512. Switched to int16_t DeviceIndex. (#119639)"
This reverts commit e0268821dd2ea0e8a51b81c0ef3b18e77f68a33d.
Reverted https://github.com/pytorch/pytorch/pull/119639 on behalf of https://github.com/huydhn due to Sorry for reverting your change but I think the Window failures are legit as they are failing now in trunk, i.e. https://hud.pytorch.org/pytorch/pytorch/commit/450339ab2d9465276e430d89010972838ba2af56 ([comment](https://github.com/pytorch/pytorch/pull/119639#issuecomment-1958428416))
