lnwallet/chancloser: enable custom payer for rbf coop close

In this commit, we enable a custom payer for the rbf coop close. This
allows us to ensure that the party that started one side of the close
flow pays the fees.

Author: Roasbeef

lnwallet/chancloser/rbf_coop_transitions.go

@@ -661,6 +661,7 @@ func (l *LocalCloseStart) ProcessEvent(event ProtocolEvent, env *Environment,
 		rawSig, closeTx, closeBalance, err := env.CloseSigner.CreateCloseProposal( //nolint:ll
 			absoluteFee, localScript, l.RemoteDeliveryScript,
 			lnwallet.WithCustomSequence(mempool.MaxRBFSequence),
+			lnwallet.WithCustomPayer(lntypes.Local),
 		)
 		if err != nil {
 			return nil, err
@@ -808,6 +809,7 @@ func (l *LocalOfferSent) ProcessEvent(event ProtocolEvent, env *Environment,
 			localSig, remoteSig, l.LocalDeliveryScript,
 			l.RemoteDeliveryScript, l.ProposedFee,
 			lnwallet.WithCustomSequence(mempool.MaxRBFSequence),
+			lnwallet.WithCustomPayer(lntypes.Local),
 		)
 		if err != nil {
 			return nil, err
@@ -903,6 +905,7 @@ func (l *RemoteCloseStart) ProcessEvent(event ProtocolEvent, env *Environment,
 		chanOpts := []lnwallet.ChanCloseOpt{
 			lnwallet.WithCustomSequence(mempool.MaxRBFSequence),
 			lnwallet.WithCustomLockTime(msg.SigMsg.LockTime),
+			lnwallet.WithCustomPayer(lntypes.Remote),
 		}
 
 		chancloserLog.Infof("responding to close w/ local_addr=%x, "+