contractcourt+lnwallet: move aux close finalization to chain watcher

We now execute the aux chan closer finalization within the chain
watcher. This is better as we don't need to rely on the remote party
being online and sending us a message. Instead we do the finalization
once the on-chain transaction has been confirmed.

lnwallet/chancloser/chancloser.go

@@ -974,33 +974,6 @@ func (c *ChanCloser) ReceiveClosingSigned( //nolint:funlen
 		}
 		c.closingTx = closeTx
 
-		// If there's an aux chan closer, then we'll finalize with it
-		// before we write to disk.
-		err = fn.MapOptionZ(
-			c.cfg.AuxCloser, func(aux AuxChanCloser) error {
-				channel := c.cfg.Channel
-				//nolint:ll
-				req := types.AuxShutdownReq{
-					ChanPoint:   c.chanPoint,
-					ShortChanID: c.cfg.Channel.ShortChanID(),
-					InternalKey: c.localInternalKey,
-					Initiator:   channel.IsInitiator(),
-					CommitBlob:  channel.LocalCommitmentBlob(),
-					FundingBlob: channel.FundingBlob(),
-				}
-				desc := types.AuxCloseDesc{
-					AuxShutdownReq:    req,
-					LocalCloseOutput:  c.localCloseOutput,
-					RemoteCloseOutput: c.remoteCloseOutput,
-				}
-
-				return aux.FinalizeClose(desc, closeTx)
-			},
-		)
-		if err != nil {
-			return noClosing, err
-		}
-
 		// Before publishing the closing tx, we persist it to the
 		// database, such that it can be republished if something goes
 		// wrong.