core/debug-control: Introspect it to export the dbus service with lg

by executing `global.context.get_debug_control().exported = true`.

This makes it possible to get access to the debug service without having
to start with `--enable-debug`.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3902>

src/core/meta-context-private.h

@@ -18,12 +18,12 @@
 
 #pragma once
 
-#include "core/meta-debug-control.h"
 #include "core/meta-private-enums.h"
 #include "core/meta-service-channel.h"
 #include "core/util-private.h"
 #include "meta/meta-backend.h"
 #include "meta/meta-context.h"
+#include "meta/meta-debug-control.h"
 #include "wayland/meta-wayland-types.h"
 
 #ifdef HAVE_PROFILER
@@ -84,5 +84,3 @@ meta_context_get_profiler (MetaContext *context);
 void meta_context_set_trace_file (MetaContext *context,
                                   const char  *trace_file);
 #endif
-
-MetaDebugControl * meta_context_get_debug_control (MetaContext *context);