Wait for inbound commitment_signed before producing tx_signatures

We only want to produce `tx_signatures` once we know that the monitor
update (either the initial one for a dual-funded channel, or a
`RenegotiatedFunding` one for a splice) has been persisted. If we
haven't received the counterparty's `commitment_signed` yet, then the
monitor update hasn't been created, leading us to pass the
`!awaiting_monitor_update` condition and produce a holder
`tx_signatures` message.

Author: wpaulino

lightning/src/ln/channelmanager.rs

@@ -9342,6 +9342,7 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 		if let Some(signing_session) = (!channel.is_awaiting_monitor_update())
 			.then(|| ())
 			.and_then(|_| channel.context.interactive_tx_signing_session.as_mut())
+			.filter(|signing_session| signing_session.has_received_commitment_signed())
 			.filter(|signing_session| signing_session.holder_tx_signatures().is_none())
 		{
 			if signing_session.has_local_contribution() {