libsysprof-analyze: add callgraph flags for thread-ids

This allows you to set a flag to show the thread id of what was recorded.

Use this to help disassociate similar threads in a process to figure out
which thread is consuming a majority of the Total time of that process.

src/libsysprof-gtk/sysprof-callgraph-view-private.h

@@ -50,6 +50,8 @@ struct _SysprofCallgraphView
   GCancellable *cancellable;
 
   guint reload_source;
+
+  guint include_threads : 1;
 };
 
 struct _SysprofCallgraphViewClass