Dedup confirmed_txs Vec

Previously, we would just push to the `confirmed_txs` `Vec`, leading to
redundant `Confirm::transactions_confirmed` calls, especially now that
we re-confirm previously disconnected spends.

Here, we ensure that we don't push additional `ConfirmTx` entries if
already one with matching `Txid` is present. This not only gets rid of
the spurious `transactions_confirmed` calls (which are harmless), but
more importantly saves us from issuing unnecessary network calls, which
improves latency.

Author: tnull

lightning-transaction-sync/src/electrum.rs

@@ -257,7 +257,7 @@ where
 
 		// First, check the confirmation status of registered transactions as well as the
 		// status of dependent transactions of registered outputs.
-		let mut confirmed_txs = Vec::new();
+		let mut confirmed_txs: Vec<ConfirmedTx> = Vec::new();
 		let mut watched_script_pubkeys = Vec::with_capacity(
 			sync_state.watched_transactions.len() + sync_state.watched_outputs.len());
 		let mut watched_txs = Vec::with_capacity(sync_state.watched_transactions.len());
@@ -305,6 +305,9 @@ where
 
 				for (i, script_history) in tx_results.iter().enumerate() {
 					let (txid, tx) = &watched_txs[i];
+					if confirmed_txs.iter().any(|ctx| ctx.tx.txid() == **txid) {
+						continue;
+					}
 					let mut filtered_history = script_history.iter().filter(|h| h.tx_hash == **txid);
 					if let Some(history) = filtered_history.next()
 					{
@@ -324,6 +327,10 @@ where
 						}
 
 						let txid = possible_output_spend.tx_hash;
+						if confirmed_txs.iter().any(|ctx| ctx.tx.txid() == txid) {
+							continue;
+						}
+
 						match self.client.transaction_get(&txid) {
 							Ok(tx) => {
 								let mut is_spend = false;

lightning-transaction-sync/src/esplora.rs

@@ -267,9 +267,12 @@ where
 		// First, check the confirmation status of registered transactions as well as the
 		// status of dependent transactions of registered outputs.
 
-		let mut confirmed_txs = Vec::new();
+		let mut confirmed_txs: Vec<ConfirmedTx> = Vec::new();
 
 		for txid in &sync_state.watched_transactions {
+			if confirmed_txs.iter().any(|ctx| ctx.tx.txid() == *txid) {
+				continue;
+			}
 			if let Some(confirmed_tx) = maybe_await!(self.get_confirmed_tx(&txid, None, None))? {
 				confirmed_txs.push(confirmed_tx);
 			}
@@ -280,6 +283,9 @@ where
 				.get_output_status(&output.outpoint.txid, output.outpoint.index as u64))?
 			{
 				if let Some(spending_txid) = output_status.txid {
+					if confirmed_txs.iter().any(|ctx| ctx.tx.txid() == spending_txid) {
+						continue;
+					}
 					if let Some(spending_tx_status) = output_status.status {
 						if let Some(confirmed_tx) = maybe_await!(self
 							.get_confirmed_tx(