vkd3d-shader/dxil: Inverse trigonometry
With tests from !364 (merged), separated out from the HLSL changes there and updated.
It is apparently unnecessary to match the SM4/5 implementation, since the AMD Windows results differ. The RADV results are a bit wrong, but Proton uses the SPIR-V GLSL extension instructions too, and no workarounds have been implemented there.
Edited by Conor McCarthy