layers:Unify image layout validation functions
layers:Unify image layout validation functions

VerifySourceImageLayout() and VerifyDestImageLayout() were nearly
identical so I generalized a couple of pieces and combined them in the
single VerifyImageLayout() function.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools