Clspv generates invalid SPIR-V for some workgroup variables

https://github.com/KhronosGroup/SPIRV-Tools/pull/6012 added validation that layout decorations are used correctly. It catches some invalid codegen in clspv related to Workgroup storage class.

Most of the logic needed is in place, but for SPIR-V 1.4 or later as it relies on OpCopyLogical. That will need extended more generally to earlier SPIR-V versions using composite extract and construct.