channeldb: store the funding transaction broadcast height for channels

This commit expands the field within the OpenChannel struct in order to
start tracking the height that the funding transaction was initially
broadcast. Other sub-systems within lnd can now use this data to give a
more accurate height hint to the ChainNotifier, or to use during the
funding workflow to decide if a channel should be forgotten after it
fails to confirm for N blocks.

channeldb/channel_test.go

@@ -654,7 +654,8 @@ func TestFetchPendingChannels(t *testing.T) {
 		Port: 18555,
 	}
 
-	if err := state.SyncPending(addr); err != nil {
+	const broadcastHeight = 99
+	if err := state.SyncPending(addr, broadcastHeight); err != nil {
 		t.Fatalf("unable to save and serialize channel state: %v", err)
 	}
 
@@ -668,6 +669,14 @@ func TestFetchPendingChannels(t *testing.T) {
 			"got %v", 1, len(pendingChannels))
 	}
 
+	// The broadcast height of the pending channel should've been set
+	// properly.
+	if pendingChannels[0].FundingBroadcastHeight != broadcastHeight {
+		t.Fatalf("broadcast height mismatch: expected %v, got %v",
+			pendingChannels[0].FundingBroadcastHeight,
+			broadcastHeight)
+	}
+
 	const openHeight = 100
 	err = cdb.MarkChannelAsOpen(pendingChannels[0].ChanID, openHeight)
 	if err != nil {
@@ -684,6 +693,11 @@ func TestFetchPendingChannels(t *testing.T) {
 		t.Fatalf("channel opening heights don't match: expected %v, "+
 			"got %v", openChans[0].OpeningHeight, openHeight)
 	}
+	if openChans[0].FundingBroadcastHeight != broadcastHeight {
+		t.Fatalf("broadcast height mismatch: expected %v, got %v",
+			openChans[0].FundingBroadcastHeight,
+			broadcastHeight)
+	}
 
 	pendingChannels, err = cdb.FetchPendingChannels()
 	if err != nil {
@@ -716,7 +730,8 @@ func TestFetchClosedChannels(t *testing.T) {
 		IP:   net.ParseIP("127.0.0.1"),
 		Port: 18555,
 	}
-	if err := state.SyncPending(addr); err != nil {
+	const broadcastHeight = 99
+	if err := state.SyncPending(addr, broadcastHeight); err != nil {
 		t.Fatalf("unable to save and serialize channel state: %v", err)
 	}