libsysprof-analyze: add GListModel of callgraph symbols

This has an indirect object (SysprofCallgraphSymbol) so that we can provide
plumbing to get the callgraph as well as the augmented data from the
indirection object.

This allows for callgraphs to show overview in the functions list which
contains the same augmentation that the descendants view does.

src/libsysprof-analyze/sysprof-callgraph-symbol-private.h

@@ -0,0 +1,29 @@
+/* sysprof-callgraph-symbol-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-callgraph.h"
+
+G_BEGIN_DECLS
+
+GListModel *_sysprof_callgraph_symbol_list_model_new (SysprofCallgraph *callgraph);
+
+G_END_DECLS