Mutter dbus
Add Mutter as possible backend to get resolutions from.
The GTK4 implementation allows to fix several bugs related to multi-monitor support under Wayland. But GTK4 is not ready for production, and may not be available on all platforms yet - typically, it is not there by default in RHEL8.
This implementation of the Mutter DBUS API allows vd_agent to get the list of monitor resolutions directly from Mutter under Gnome. It is limited to Mutter-based environment though - under KDE with Wayland for instance, vd_agent will default to X11 library and still have the same bugs.
This is a default, limited fix, usable on platforms where GTK4 is not an option.
- Fixes BZ#1824610
- Partial fix for BZ#1790904: with this patch, an additional (unneeded) window is still opened, BUT mouse events are now correctly handled on the expected window. This window being opened is not caused by the agent, so the fix will need to be done in another component.