DX 12 support and dynamic resolution scaling

[Zod1234]

first, thanks for continuing this project. I'm hoping dx12 support can be worked on. that might be a big ask, as my understanding is dx 12 has significant changes over 11, but if it can be done that would be great.

I see you have dynamic ffr; normally I'm not a big fan of ffr, but I'll give this a try. but I'd like to see dynamic image scaling on the full image and not just foveated. I think steamvr used to have issues dynamically changing the resolution with the slider, but that seems to work with most games now. I'm wondering if that can be used to dynamically change resolution based on target refresh rate.

just to mention a game where your vrperfkit doesn't work is the forest. to be fair, it doesn't work with folger's either. but it does work with openvr_far, with his prior image scaler.