lntest+itest: add new method AssertChannelInGraph

This commit replaces `AssertTopologyChannelOpen` with
`AssertChannelInGraph`, which asserts a given channel edge is found.
`AssertTopologyChannelOpen` only asserts a given edge has been received
via the topology subscription, while we need to make sure the channel is
in the graph before continuing our tests.

itest/lnd_misc_test.go

@@ -172,10 +172,10 @@ func testSphinxReplayPersistence(ht *lntest.HarnessTest) {
 	invoiceResp := dave.RPC.AddInvoice(invoice)
 
 	// Wait for all channels to be recognized and advertized.
-	ht.AssertTopologyChannelOpen(carol, chanPoint)
-	ht.AssertTopologyChannelOpen(dave, chanPoint)
-	ht.AssertTopologyChannelOpen(carol, chanPointFC)
-	ht.AssertTopologyChannelOpen(fred, chanPointFC)
+	ht.AssertChannelInGraph(carol, chanPoint)
+	ht.AssertChannelInGraph(dave, chanPoint)
+	ht.AssertChannelInGraph(carol, chanPointFC)
+	ht.AssertChannelInGraph(fred, chanPointFC)
 
 	// With the invoice for Dave added, send a payment from Fred paying
 	// to the above generated invoice.
@@ -417,7 +417,7 @@ func testMaxPendingChannels(ht *lntest.HarnessTest) {
 		// Ensure that the funding transaction enters a block, and is
 		// properly advertised by Alice.
 		ht.AssertTxInBlock(block, fundingTxID)
-		ht.AssertTopologyChannelOpen(alice, fundingChanPoint)
+		ht.AssertChannelInGraph(alice, fundingChanPoint)
 
 		// The channel should be listed in the peer information
 		// returned by both peers.