[HLSL] add log library functions

This change exposes the log library functions for HLSL,excluding long, int, and long long doubles. The log functions are supported for all scalar, vector, and matrix types.
Long and long long double support is missing in this patch because those types
don't exist in HLSL. Int is missing because the log functions only work on floating type arguments.

The full documentation of the HLSL log functions are available here:
https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-log
https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-log2
https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-log10

Reviewed By: python3kgae

Differential Revision: https://reviews.llvm.org/D144120