libsysprof-profile: add SysprofDiagnostic to recordings

This allows instruments to record a diagnostic and have it land as an
object in a GListModel of diagnostics available to the API consumer.

Such items may be used by recording UI to display issues with the recording
to the user.

src/libsysprof-profile/sysprof-diagnostic-private.h

@@ -0,0 +1,31 @@
+/* sysprof-diagnostic-private.h
+ *
+ * Copyright 2023 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include "sysprof-diagnostic.h"
+
+G_BEGIN_DECLS
+
+SysprofDiagnostic *_sysprof_diagnostic_new (char     *domain,
+                                            char     *message,
+                                            gboolean  fatal);
+
+G_END_DECLS