Expose SamplerAddress::MirrorClampToEdge

[kvark]

This is required for gfx-rs/gfx#2100 support

[grovesNL]

I looked into this briefly to check if it's already available upstream, but it's unclear how this should be handled because it doesn't exist as an SPIR-V sampler addressing mode. Is there something else we could do here?

[kvark]

This is a bit nasty. I wasn't able to find anything either :(
It looks like SPIR-V is missing an extension for mirror-clamp addressing in constant samplers.
cc @dneto0