mesa_interface: Move out of GL/internal/

Move it into src/gallium/include/ to make it absolutely clear this is a Mesa detail.
While we're at it, clean up its include sites, including some places
where we can just include kopper_interface.h instead since it includes
mesa_interface.h as its first act.

Acked-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28378>

src/util/u_gralloc/meson.build

@@ -30,7 +30,7 @@ endif
 _libmesa_u_gralloc = static_library(
   '_mesa_u_gralloc',
   [files_u_gralloc],
-  include_directories : [inc_include, inc_util],
+  include_directories : [inc_gallium, inc_include, inc_util],
   c_args : c_args_for_u_gralloc,
   cpp_args : cpp_args_for_u_gralloc,
   override_options : options_for_u_gralloc,

src/util/u_gralloc/u_gralloc.h

@@ -17,7 +17,7 @@ extern "C" {
 #include <stdbool.h>
 
 #include "util/macros.h"
-#include "GL/internal/mesa_interface.h"
+#include "mesa_interface.h"
 
 struct u_gralloc;