Use channel ID over funding outpoint to track monitors in ChannelManager

As motivated by the previous commit, we do some of the same work here at
the `ChannelManager` level instead. Unfortunately, we still need to
track the funding outpoint to support downgrades by writing the in
flight monitor updates as two separate TLVs, one using the channel IDs,
and the other using the funding outpoints. Once we are willing to stop
supporting downgrades past this version, we can fully drop it.

Author: wpaulino

fuzz/src/chanmon_consistency.rs

@@ -173,7 +173,6 @@ struct LatestMonitorState {
 	/// A set of (monitor id, serialized `ChannelMonitor`)s which we're currently "persisting",
 	/// from LDK's perspective.
 	pending_monitors: Vec<(u64, Vec<u8>)>,
-	funding_txo: OutPoint,
 }
 
 struct TestChainMonitor {
@@ -219,14 +218,12 @@ impl chain::Watch<TestChannelSigner> for TestChainMonitor {
 		let mut ser = VecWriter(Vec::new());
 		monitor.write(&mut ser).unwrap();
 		let monitor_id = monitor.get_latest_update_id();
-		let funding_txo = monitor.get_funding_txo().0;
 		let res = self.chain_monitor.watch_channel(channel_id, monitor);
 		let state = match res {
 			Ok(chain::ChannelMonitorUpdateStatus::Completed) => LatestMonitorState {
 				persisted_monitor_id: monitor_id,
 				persisted_monitor: ser.0,
 				pending_monitors: Vec::new(),
-				funding_txo,
 			},
 			Ok(chain::ChannelMonitorUpdateStatus::InProgress) => {
 				panic!("The test currently doesn't test initial-persistence via the async pipeline")
@@ -716,7 +713,7 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 			let mut old_monitors = $old_monitors.latest_monitors.lock().unwrap();
 			for (channel_id, mut prev_state) in old_monitors.drain() {
 				monitors.insert(
-					prev_state.funding_txo,
+					channel_id,
 					<(BlockHash, ChannelMonitor<TestChannelSigner>)>::read(
 						&mut Cursor::new(&prev_state.persisted_monitor),
 						(&*$keys_manager, &*$keys_manager),
@@ -731,8 +728,8 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 				chain_monitor.latest_monitors.lock().unwrap().insert(channel_id, prev_state);
 			}
 			let mut monitor_refs = new_hash_map();
-			for (outpoint, monitor) in monitors.iter() {
-				monitor_refs.insert(*outpoint, monitor);
+			for (channel_id, monitor) in monitors.iter() {
+				monitor_refs.insert(*channel_id, monitor);
 			}
 
 			let read_args = ChannelManagerReadArgs {
@@ -755,9 +752,9 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 					.1,
 				chain_monitor.clone(),
 			);
-			for (_, mon) in monitors.drain() {
+			for (channel_id, mon) in monitors.drain() {
 				assert_eq!(
-					chain_monitor.chain_monitor.watch_channel(mon.channel_id(), mon),
+					chain_monitor.chain_monitor.watch_channel(channel_id, mon),
 					Ok(ChannelMonitorUpdateStatus::Completed)
 				);
 			}