layers: Use common ext lists in unique_objects
layers: Use common ext lists in unique_objects

Change-Id: I6d3ac8921dcc648df606040794029733c0516eeb

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