lnrpc+lnrpc/routerrpc: add a new TLV record field to the Hop proto

In this commit, we add a new field to the Hop proto to allow callers to
be able to specify TLV records for the SendToRoute call, and also to be
able to display TLV records that were used during regular path finding.

We also update SendPayment to support dest TLV records.

lnrpc/routerrpc/router_backend_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing"
 	"github.com/lightningnetwork/lnd/routing/route"
+	"github.com/lightningnetwork/lnd/tlv"
 
 	"github.com/lightningnetwork/lnd/lnrpc"
 )
@@ -77,6 +78,7 @@ func testQueryRoutes(t *testing.T, useMissionControl bool) {
 
 	findRoute := func(source, target route.Vertex,
 		amt lnwire.MilliSatoshi, restrictions *routing.RestrictParams,
+		_ []tlv.Record,
 		finalExpiry ...uint16) (*route.Route, error) {
 
 		if int64(amt) != request.Amt*1000 {