dzn: Support inverted min/maxDepth in VkViewport
D3D12 doesn't allow viewport.MinDepth > viewport.MaxDepth. We have to lower the depth inversion shader-side to support this case. While at it, add support negative viewport height.
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D3D12 doesn't allow viewport.MinDepth > viewport.MaxDepth. We have to lower the depth inversion shader-side to support this case. While at it, add support negative viewport height.