Add SPIR-V backend support for the HLSL SV_DispatchThreadID semantic
attribute, which is lowered to a @llvm.dx.thread.id intrinsic in LLVM
IR. In the SPIR-V backend, this is now correctly translated to a
`GlobalInvocationId` builtin variable.
Fixes#82534
Support SV_DispatchThreadID attribute.
Translate it into dx.thread.id in clang codeGen.
Reviewed By: beanz, aaron.ballman
Differential Revision: https://reviews.llvm.org/D133983