Add MVKPhysicalDeviceMetalFeatures::multisampleLayeredRendering feature.
MVKCmdClearAttachments shader don't include [[render_target_array_index]] if multisample
and multisampleLayeredRendering is false.
Refactor validation of VkImageCreateInfo when creating an MVKImage.
Validate MVKImage multisample layered array attachments require multisampleLayeredRendering.