[Clang][OpenCL][AMDGPU] Add tests for optnone attribute assigned to OpenCL Kernels (#138849)
OpenCL Kernel stubs should be always inlined
https://github.com/llvm/llvm-project/pull/137769
In case optnone is assigned to kernel, respective stub should not be
assigned alwaysinline, we add test for the same.
Co-authored-by: anikelal <anikelal@amd.com>