Goes atop MR 372, 403 and 388. The last six commits belong to this MR.
-- v5: vkd3d-shader/dxil: Implement the DXIL EXTRACTVAL instruction. vkd3d-shader/dxil: Implement DX instruction CBufferLoadLegacy. vkd3d-shader/dxil: Implement DX instruction CreateHandle. vkd3d-shader/dxil: Read CBV descriptors. vkd3d-shader/spirv: Align constant buffer sizes to 16 bytes.