layers:Use make_shared for share_ptr creation
layers:Use make_shared for share_ptr creation

std::make_shared is more efficient for shared_ptr creation, using a
single heap allocation for both the object and control logic, vs. two
separate allocations of using "new" w/ shared_ptr constructor.

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