Function forward_legacy_timeout_votes 

pub async fn forward_legacy_timeout_votes<T: NodeType>(
    legacy_event_rx: InactiveReceiver<Event<T>>,
    client_api: ClientApi<T>,
    upgrade_lock: UpgradeLock<T>,
    queue_len: Option<Arc<dyn Gauge>>,
)

Forward legacy TimeoutVote2 events into the new-protocol timeout collectors so the first new leader can form TC2 at the boundary.