Syncer client: many fns impl for SyncerState, should be impl for SyncerTasks

[zkao]

[zkao]

e.g.,

    pub fn is_watched_tx(&self, tx_label: &TxLabel) -> bool {
        self.tasks.watched_txs.values().any(|tx| tx == tx_label)
    }

[sedited]

Would be kind of inconvenient for the call sites of the SyncerState to indirect these calls on level deeper to the SyncerTasks. I'm closing this for this reason.