I've turned on the `Resolve` cap for stencil-only formats, even though
no version of the Metal Feature Set tables lists them as supporting
multisample resolve. Obviously, if they couldn't be resolve
destinations, the stencil-resolve filter that was introduced in Metal
2.1 wouldn't work. I don't know if the platforms and feature sets where
I've turned the bit on is accurate, though. Wider testing is needed.
Because Apple families 1 and 2 don't support depth/stencil resolve at
all, I've disabled the extension for those families. Since sample-zero
resolution is a required feature of Vulkan 1.2, this means we won't be
able to support 1.2 on those devices. If there's demand, we could
possibly have a compute pass which does sample-zero resolution.
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