lnd: add support for pushing funds as part of channel funding

This commit adds daemon level support for pushing funds as part of the
single funder channel workflow. This new feature allows the user to
open a channel and simultaneously make a channel at the same time which
can improve the UX when setting up a channel for the first time.

server.go

@@ -566,6 +566,8 @@ type openChanReq struct {
 	localFundingAmt  btcutil.Amount
 	remoteFundingAmt btcutil.Amount
 
+	pushAmt btcutil.Amount
+
 	numConfs uint32
 
 	updates chan *lnrpc.OpenStatusUpdate
@@ -777,20 +779,20 @@ func (s *server) ConnectToPeer(addr *lnwire.NetAddress) (int32, error) {
 // OpenChannel sends a request to the server to open a channel to the specified
 // peer identified by ID with the passed channel funding paramters.
 func (s *server) OpenChannel(peerID int32, nodeKey *btcec.PublicKey,
-	localAmt, remoteAmt btcutil.Amount,
+	localAmt, pushAmt btcutil.Amount,
 	numConfs uint32) (chan *lnrpc.OpenStatusUpdate, chan error) {
 
 	errChan := make(chan error, 1)
 	updateChan := make(chan *lnrpc.OpenStatusUpdate, 1)
 
 	req := &openChanReq{
-		targetPeerID:     peerID,
-		targetPubkey:     nodeKey,
-		localFundingAmt:  localAmt,
-		remoteFundingAmt: remoteAmt,
-		numConfs:         numConfs,
-		updates:          updateChan,
-		err:              errChan,
+		targetPeerID:    peerID,
+		targetPubkey:    nodeKey,
+		localFundingAmt: localAmt,
+		pushAmt:         pushAmt,
+		numConfs:        numConfs,
+		updates:         updateChan,
+		err:             errChan,
 	}
 
 	s.queries <- req