[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.