[SPIR-V] Implement SPV_KHR_fma extension (#173057)
The extension adds support for the `OpFmaKHR` instruction, which
provides a native SPIR-V instruction for fused multiply-add operations
as an alternative to using OpenCL.std::Fma extended instruction.
Translate both LLVM fma intrinsics as well as OCL builtins to `OpFmaKHR`
if the extension is available.
Specification:
https://github.khronos.org/SPIRV-Registry/extensions/KHR/SPV_KHR_fma.html
