meson: use a feature option for dri3

This removes the deprecated 'true' and 'false' options, and uses a meson
feature, requiring significantly less code.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20409>

meson_options.txt

@@ -46,9 +46,7 @@ option(
 
 option(
   'dri3',
-  type : 'combo',
-  value : 'auto',
-  choices : ['auto', 'true', 'false', 'disabled', 'enabled'],
+  type : 'feature',
   description : 'enable support for dri3'
 )
 option(