[HLSL] Implementation of the frac intrinsic (#83315)
This change implements the frontend for #70099
Builtins.td - add the frac builtin
CGBuiltin.cpp - add the builtin to DirectX intrinsic mapping
hlsl_intrinsics.h - add the frac api
SemaChecking.cpp - add type checks for builtin
IntrinsicsDirectX.td - add the frac intrinsic
The backend changes for this are going to be very simple:
https://github.com/llvm/llvm-project/commit/f309a0eb558b65dfaff0d1d23b7d07fb07e27121
They were not included because llvm/lib/Target/DirectX/DXIL.td is going
through a major refactor.
