This extension allows multiple device memory objects to be bound in one
call. It also provides extensible versions of the memory binding calls.
It is a prerequisite for both the `VK_KHR_device_group` and
`VK_KHR_sampler_ycbcr_conversion` extensions.
The `VK_IMAGE_CREATE_ALIAS_BIT`, also added in this extension, would be
more interesting if we used `MTLHeap` objects for device memory, since
that would determine whether or not we would make images aliasable.
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