Delegate on the MetaInputMapper all matching of inputs and outputs,
including configuration. Other secondary aspects, like output
aspect ratio for tablet letterbox mode, or toggling attached devices
with power saving changes, are also moved here.
This makes MetaInputSettings independent of MetaMonitorManager,
all interaction with it happens indirectly via public API entrypoints.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1403>