tests:Make ImageBarrierSubpassConflict test
tests:Make ImageBarrierSubpassConflict test

Move testcase out of RenderPassBarrierConflicts, where it was a bit
muddled and confusing, into ImageBarrierSubpassConflict where it can
stand alone and is easier to follow.

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers