Add command line support which enables the following behavior:
- Remap discard
Map discard to DemoteToHelperInvocation for HLSL shaders. Map to
OpTerminateInvocation for GLSL shaders.
- Decorate HelperInvocation with Volatile
- Use localSizeId for execution mode
WorkGroupSize is deprecated in spirv1.6
Also update known goods to SPIRV 1.6
