nvk: Enable the new UAPI

We also add a meson option to disable it and re-enable the legacy API.
This code probably won't last long but it gives developers the option.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24326>

meson.build

@@ -261,6 +261,12 @@ with_any_intel = [
 ].contains(true)
 with_any_nouveau = with_gallium_nouveau or with_nouveau_vk
 
+if with_nouveau_vk and get_option('nvk-legacy-uapi')
+  pre_args += '-DNVK_NEW_UAPI=0'
+else
+  pre_args += '-DNVK_NEW_UAPI=1'
+endif
+
 if with_swrast_vk and not with_gallium_softpipe
   error('swrast vulkan requires gallium swrast')
 endif