lnwallet: thread through tx conf details in ChannelReservation.DispatchChan()

This commit slightly modifies the channel reservation workflow to
expose the new information conerning the exact confirmation location of
the channel provided by the ChainNotifier. The DispatchChan() method of
the ChannelReservation now also returns the blockHeight and txIndex
where the transaction was ultimately confirmed. This information will
be needed by the fundingManager so it can properly generate the
authenticated channel announcement proofs.

lnwallet/wallet.go

@@ -934,6 +934,17 @@ func (l *LightningWallet) handleSingleContribution(req *addSingleContributionMsg
 	return
 }
 
+// openChanDetails contains a "finalized" channel which can be considered
+// "open" according to the requested confirmation depth at reservation
+// initialization. Additionally, the struct contains additional details
+// pertaining to the exact location in the main chain in-which the transaction
+// was confirmed.
+type openChanDetails struct {
+	channel     *LightningChannel
+	blockHeight uint32
+	txIndex     uint32
+}
+
 // handleFundingCounterPartySigs is the final step in the channel reservation
 // workflow. During this step, we validate *all* the received signatures for
 // inputs to the funding transaction. If any of these are invalid, we bail,
@@ -1212,7 +1223,9 @@ func (l *LightningWallet) handleChannelOpen(req *channelOpenMsg) {
 	channel, _ := NewLightningChannel(l.Signer, l.ChainIO, l.chainNotifier,
 		res.partialState)
 
-	res.chanOpen <- channel
+	res.chanOpen <- &openChanDetails{
+		channel: channel,
+	}
 	req.err <- nil
 }
 
@@ -1231,9 +1244,13 @@ func (l *LightningWallet) openChannelAfterConfirmations(res *ChannelReservation)
 
 	// Wait until the specified number of confirmations has been reached,
 	// or the wallet signals a shutdown.
+	var (
+		confDetails *chainntnfs.TxConfirmation
+		ok          bool
+	)
 out:
 	select {
-	case _, ok := <-confNtfn.Confirmed:
+	case confDetails, ok = <-confNtfn.Confirmed:
 		// Reading a falsey value for the second parameter indicates that
 		// the notifier is in the process of shutting down. Therefore, we
 		// don't count this as the signal that the funding transaction has
@@ -1253,7 +1270,11 @@ out:
 	// TODO(roasbeef): CreationTime once tx is 'open'
 	channel, _ := NewLightningChannel(l.Signer, l.ChainIO, l.chainNotifier,
 		res.partialState)
-	res.chanOpen <- channel
+	res.chanOpen <- &openChanDetails{
+		channel:     channel,
+		blockHeight: confDetails.BlockHeight,
+		txIndex:     confDetails.TxIndex,
+	}
 }
 
 // selectCoinsAndChange performs coin selection in order to obtain witness