contractcourt: update chain watcher to understand the taproot pkscript

In this commit, we update the chain watcher to be able to generate the
correct pkScript so it can register for confirmation and spend
notifications for taproot channels.

contractcourt/chain_watcher.go

@@ -287,17 +287,32 @@ func (c *chainWatcher) Start() error {
 		}
 	}
 
-	localKey := chanState.LocalChanCfg.MultiSigKey.PubKey.SerializeCompressed()
-	remoteKey := chanState.RemoteChanCfg.MultiSigKey.PubKey.SerializeCompressed()
-	multiSigScript, err := input.GenMultiSigScript(
-		localKey, remoteKey,
+	localKey := chanState.LocalChanCfg.MultiSigKey.PubKey
+	remoteKey := chanState.RemoteChanCfg.MultiSigKey.PubKey
+
+	var (
+		pkScript []byte
+		err      error
 	)
-	if err != nil {
-		return err
-	}
-	pkScript, err := input.WitnessScriptHash(multiSigScript)
-	if err != nil {
-		return err
+	if chanState.ChanType.IsTaproot() {
+		pkScript, _, err = input.GenTaprootFundingScript(
+			localKey, remoteKey, 0,
+		)
+		if err != nil {
+			return err
+		}
+	} else {
+		multiSigScript, err := input.GenMultiSigScript(
+			localKey.SerializeCompressed(),
+			remoteKey.SerializeCompressed(),
+		)
+		if err != nil {
+			return err
+		}
+		pkScript, err = input.WitnessScriptHash(multiSigScript)
+		if err != nil {
+			return err
+		}
 	}
 
 	spendNtfn, err := c.cfg.notifier.RegisterSpendNtfn(
@@ -834,6 +849,9 @@ func (c *chainWatcher) handlePossibleBreach(commitSpend *chainntnfs.SpendDetail,
 	}
 
 	// Create an AnchorResolution for the breached state.
+	//
+	// TODO(roasbeef): make keyring for taproot chans to pass in instead of
+	// nil
 	anchorRes, err := lnwallet.NewAnchorResolution(
 		c.cfg.chanState, commitSpend.SpendingTx, nil,
 	)