test: add comprehensive integration tests for on-chain HTLC handling

In this commit, we add 6 new integration tests to test the various
actions that may need to be performed when either side goes on-chain to
fully resolve HTLC’s. Many of the tests are mirrors of each other as
they test sweeping/resolving HTLC’s from both commitment transactions.

config.go

@@ -42,6 +42,8 @@ const (
 	defaultNoEncryptWallet    = false
 	defaultTrickleDelay       = 30 * 1000
 
+	defaultBroadcastDelta = 10
+
 	// minTimeLockDelta is the minimum timelock we require for incoming
 	// HTLCs on our channels.
 	minTimeLockDelta = 4