It's not really a backend thing, and we'll want to profile e.g. loading the backend too, so create it very early and destroy it very late and let MetaContextMain own it. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2678>
This exposes the /org/gnome/Sysprof3/Profiler object inside Mutter to allow initiating a Sysprof capture. https://gitlab.gnome.org/GNOME/mutter/merge_requests/197