Feature request: Enable binding to a specific IOSurface plane

[yuhsianglu]

from vkUseIOSurfaceMVK() to MVKImage::newMTLTexture(), the IOSurface plane binding is hardcoded to 0, which is not handy if the IOSurface is created with planar format e.g. the IOSurface created for VideoToolBox hw encoding. or maybe integrate it with vk multi-planar format like VK_FORMAT_G8_B8_R8_3PLANE_420_UNORM?