Since we cache already all the KMS parameters we care about let's check at
each device update if anything has really changed and only in such case
emit a resources-changed signal.
In this way we can also filter out the DRM parameters that when changed
don't require a full monitors rebuild.
Examples are the gamma settings or the privacy screen parameters, that
emits an udev "hotplug" event when changed, but we want to register those
only when we handle the changed property.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>
This contains a copy of a drmModeModeInfo, describing a mode. It also
has an unused pointer to the impl device it is associated with. It'll
later be used to get a blob ID for the mode.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
