[clang] [HLSL] Implementation of the fmod intrinsic (PR #108849)

[Farzon Lotfi via cfe-commits]

farzonl wrote:

change the title of this PR to remove the word intrinsic. That word has a specific meaning in LLVM and folks might get confused. Something like: `[HLSL] Implementation of the fmod API` 

https://github.com/llvm/llvm-project/pull/108849