[HLSL] Implement WaveReadLaneAt intrinsics

[inbelic]

- create a clang built-in
- add mapping to dxil opcode
- add lowering to SPIR-V GroupNonUniformShuffle with Scope = 2
  (Group)
- add sema checks
- add related tests

[inbelic]

Whoops, will remove when I address other comments

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff f3c408d1726f6a921212faf68085f68bf8533f0c 0320a5acec2565608cb91b271f6cda49fc364bb7 --extensions cpp,h -- clang/lib/CodeGen/CGBuiltin.cpp clang/lib/CodeGen/CGHLSLRuntime.h clang/lib/Headers/hlsl/hlsl_intrinsics.h clang/lib/Sema/SemaHLSL.cpp llvm/lib/Target/DirectX/DXILOpBuilder.cpp llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp llvm/utils/TableGen/DXILEmitter.cpp

View the diff from clang-format here.

diff --git a/clang/lib/Headers/hlsl/hlsl_intrinsics.h b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
index f3707d8076..a7bdc353ae 100644
--- a/clang/lib/Headers/hlsl/hlsl_intrinsics.h
+++ b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
@@ -2020,7 +2020,7 @@ __attribute__((convergent)) bool WaveIsFirstLane();
 template <typename T>
 _HLSL_AVAILABILITY(shadermodel, 6.0)
 _HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_read_lane_at)
-__attribute__((convergent)) T WaveReadLaneAt(T, int32_t);
+    __attribute__((convergent)) T WaveReadLaneAt(T, int32_t);
 
 //===----------------------------------------------------------------------===//
 // sign builtins

[inbelic]

IIUC, an HLSL wave corresponds to the SPIR-V workgroup scope, which is denoted as 2.