lntest+itest: start flattening the multi-hop tests

Starting from this commit, we begin the process of flattening the
multi-hop itests to make them easier to be maintained. The tests are
refactored into their own test cases, with each test focusing on testing
one channel type. This is necessary to save effort for future
development.

These tests are also updated to reflect the new `blockbeat` behavior.

itest/list_on_test.go

@@ -153,10 +153,6 @@ var allTestCases = []*lntest.TestCase{
 		Name:     "addpeer config",
 		TestFunc: testAddPeerConfig,
 	},
-	{
-		Name:     "multi hop htlc local timeout",
-		TestFunc: testMultiHopHtlcLocalTimeout,
-	},
 	{
 		Name:     "multi hop local force close on-chain htlc timeout",
 		TestFunc: testMultiHopLocalForceCloseOnChainHtlcTimeout,
@@ -715,3 +711,8 @@ var allTestCases = []*lntest.TestCase{
 		TestFunc: testQuiescence,
 	},
 }
+
+func init() {
+	// Register subtests.
+	allTestCases = append(allTestCases, multiHopForceCloseTestCases...)
+}