[Clang][OpenCL][AMDGPU] Add tests for optnone attribute assigned to OpenCL Kernels (#138849)

OpenCL Kernel stubs should be always inlined
#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 <[email protected]>

Author: lalaniket8