[HLSL] Implement the `degrees` intrinsic (#111209)
- add degrees builtin
- link degrees api in hlsl_intrinsics.h
- add degrees intrinsic to IntrinsicsDirectX.td
- add degrees intrinsic to IntrinsicsSPIRV.td
- add lowering from clang builtin to dx/spv intrinsics in CGBuiltin.cpp
- add semantic checks to SemaHLSL.cpp
- add expansion of directx intrinsic to llvm fmul for DirectX in
DXILIntrinsicExpansion.cpp
- add mapping to spir-v intrinsic in SPIRVInstructionSelector.cpp
- add test coverage:
- degrees.hlsl -> check hlsl lowering to dx/spv degrees intrinsics
- degrees-errors.hlsl/half-float-only-errors -> check semantic warnings
- hlsl-intrinsics/degrees.ll -> check lowering of spir-v degrees
intrinsic to SPIR-V backend
- DirectX/degrees.ll -> check expansion and scalarization of directx
degrees intrinsic to fmul
Resolves #99104
