zink: add provoking vertex mode lowering
This MR adds a fallback for when VK_EXT_provoking_vertex is missing.
It emulates provoking vertex mode with a geometry shader
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The migration is almost done, at least the rest should happen in the background. There are still a few technical difference between the old cluster and the new ones, and they are summarized in this issue. Please pay attention to the TL:DR at the end of the comment.
This MR adds a fallback for when VK_EXT_provoking_vertex is missing.
It emulates provoking vertex mode with a geometry shader