Add some profiling labels

Add profiler labels for things like GObject property getters and setters and method calls. This way glue overhead and inner calls are correctly grouped and shown in stack traces.

Before:

After:

This MR combined with https://gitlab.gnome.org/YaLTeR/sysprof/-/tree/recursive-calls makes Shell profiles more telling.

cc @verdre who has already put this to good use for some Shell improvements.