Update OnchainTxHandler channel parameters on renegotiated funding locked

The `ChannelMonitor` now tracks its own set of channel parameters, but
in the event they change after a splice, we want to ensure they are
updated accordingly at the `OnchainTxHandler` level as well in case the
user downgrades after a locked splice has already occurred.

Author: wpaulino

lightning/src/chain/channelmonitor.rs

@@ -4049,6 +4049,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 
 		mem::swap(&mut self.funding, &mut new_funding);
 		self.onchain_tx_handler.update_after_renegotiated_funding_locked(
+			self.funding.channel_parameters.clone(),
 			self.funding.current_holder_commitment_tx.clone(),
 			self.funding.prev_holder_commitment_tx.clone(),
 		);

lightning/src/chain/onchaintx.rs

@@ -1236,11 +1236,14 @@ impl<ChannelSigner: EcdsaChannelSigner> OnchainTxHandler<ChannelSigner> {
 		self.prev_holder_commitment = Some(replace(&mut self.holder_commitment, tx));
 	}
 
-	/// Replaces the current/prev holder commitment transactions spending the currently confirmed
-	/// funding outpoint with those spending the new funding outpoint.
+	/// Replaces all the data pertaining to the currently locked funding transaction after a new
+	/// funding transaction has been renegotiated and locked.
 	pub(crate) fn update_after_renegotiated_funding_locked(
-		&mut self, current: HolderCommitmentTransaction, prev: Option<HolderCommitmentTransaction>,
+		&mut self, channel_parameters: ChannelTransactionParameters,
+		current: HolderCommitmentTransaction, prev: Option<HolderCommitmentTransaction>,
 	) {
+		self.channel_value_satoshis = channel_parameters.channel_value_satoshis;
+		self.channel_transaction_parameters = channel_parameters;
 		self.holder_commitment = current;
 		self.prev_holder_commitment = prev;
 	}