/// Called to determine the relative update priority of an ref_object.
///
/// All objects that are in scope and that have out of date states are queried and sorted by priority before being updated. If there is not enough room in a single packet for all out of date objects, the skipped objects will have an incremented update_skips the next time that connection prepares to send a packet. Typically the update priority is scaled by update_skips so that as data becomes stale, it becomes more of a priority to update.