anv,radv: Implement vkAcquireNextImage2

This was added as part of 1.1 but it's very hard to track exactly what
extension added it.  In any case, we should implement it.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Dave Airlie <Airlied@redhat.com>
(cherry picked from commit ab80889e)