[SPIRV][HLSL] Implement `frac` lowering

[farzonl]

• Create a frac intrinsic for spirv use the hlsl intrinsic switching to swap on target.

update the frac.hlsl unit tests:

llvm-project/clang/test/CodeGenHLSL/builtins/frac.hlsl

Line 2 in 1e6ce5e

// RUN: dxil-pc-shadermodel6.3-library %s -fnative-half-type \

example:
https://shader-playground.timjones.io/020254826814c6bfb01e671c08c15db4

and implement the OpExtInst Fract Lowering:
%13 = OpExtInst %v4float %1 Fract %12
https://registry.khronos.org/SPIR-V/specs/1.0/GLSL.std.450.html#Fract

[damyanp]

Need resolution to #87367 before doing this.

[davidcook-msft]

Issue to be re-evaluated and updated

[farzonl]

@davidcook-msft this ticket is now just add frac support for spirv. Should just be create a spirv intrinsic use our target switching so hlsl picks the right intrinsic. then update the existing tests and add new spirv backend tests

[tex3d]

Sign me up!