D3D12

This fixes some stuff for D3D11 too (swapchain leak) and turns off depth textures in d3d11 because they never worked, I just didn't see the error message in the debug console.

This gets D3D12 going, without depth textures by default. Works with hello xr on Intel and NVIDIA. I think d3d12 openxr conformance ran OK, but D3D11 conformance insists on receiving at least one depth format so that fails. Follow-up will fix depth textures, hopefully. Just makes no sense to keep holding this back since apparently d3d11 never had them yet.