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/mapi/glapi/meson.build

@@ -63,7 +63,7 @@ endif
 libglapi_bridge = static_library(
   'glapi_bridge',
   bridge_glapi_files,
-  include_directories : [inc_mesa, inc_include, inc_src, inc_mapi],
+  include_directories : [inc_mesa, inc_include, inc_src, inc_mapi, inc_gallium],
   c_args : [c_msvc_compat_args, bridge_glapi_args],
   dependencies : [dep_thread, dep_selinux, idep_mesautil],
   build_by_default : false,
@@ -75,7 +75,7 @@ else
   libglapi_static = static_library(
     'glapi_static',
     static_glapi_files,
-    include_directories : [inc_mesa, inc_include, inc_src, inc_mapi],
+    include_directories : [inc_mesa, inc_include, inc_src, inc_mapi, inc_gallium],
     c_args : [c_msvc_compat_args, static_glapi_args],
     dependencies : [dep_thread, dep_selinux, idep_mesautil],
     build_by_default : false,
@@ -90,7 +90,7 @@ if with_any_opengl and not with_shared_glapi and with_tests and not with_platfor
     executable(
       'glapi_static_check_table',
       ['tests/check_table.cpp', glapitable_h],
-      include_directories : [inc_include, inc_src, inc_mesa, inc_mapi],
+      include_directories : [inc_include, inc_src, inc_mesa, inc_mapi, inc_gallium],
       link_with : [libglapi_static],
       dependencies : [idep_gtest, dep_thread],
     ),