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-debug-control-private.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2023 Red Hat
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#pragma once
+
+#include "meta/meta-debug-control.h"
+
+gboolean meta_debug_control_is_linear_blending_forced (MetaDebugControl *debug_control);
+
+gboolean meta_debug_control_is_hdr_enabled (MetaDebugControl *debug_control);