Function settle 

async fn settle(
    changes: &mut Receiver<FleetSnapshot>,
    token: &CancellationToken,
    timing: &Timing,
) -> bool

Wait until the agents, kinds and channel count have been quiet for DEBOUNCE, at most a publish interval in all. A change of states alone does not restart the wait: busy agents would otherwise hold a new agent back for the full interval. false on shutdown.