We can implement glPolygonMode(GL_FRONT_AND_BACK, ...) natively. What we can't
implement natively are two-sided polygon modes. For that Apple has a nontrivial
lowering which I don't feel the need to implement unless someone actually hits a
workload other than Piglit that uses it.
Vulkan requires only one-sided polygon modes (so this is sufficient there), and
GLES doesn't have polygon modes at all. If an app hits the unimplemented case,
throw a warning like Zink does.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20017>