zink: handle edgeflags

zink: handle edgeflags

Vulkan has no support for edgeflags.

If the user has a geometry shader bound nothing needs to be done as edgeflags
don't work with them, otherwise a geometry shader that emulates them
is generated.

Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21238>