Goes atop !436. The last three commits belong to this MR.
-- v5: vkd3d-shader/dxil: Implement the DXIL CMP2 instruction. vkd3d-shader/spirv: Support orderedness inversion in comparison instructions. vkd3d-shader/spirv: Support bool result in spirv_compiler_emit_comparison_instruction(). vkd3d-shader/dxil: Implement the DXIL CAST instruction.