Currently, when using `-display dbus,gl=on` all updates to the client
become "full scanout" updates, meaning there is no way for the client to
limit damage regions to the display server.

Instead of using an "update count", this patch tracks the damage region
and propagates it to the client.

This was less of an issue when clients were using GtkGLArea for
rendering,
as you'd be doing full-surface redraw. To be efficient, the client needs
both a DMA-BUF and the damage region to be updated.

Co-authored-by: Christian Hergert <chergert@redhat.com>
Signed-off-by: Bilal Elmoussaoui <belmouss@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230814125802.102160-1-belmouss@redhat.com>