multi: remove debug invoices

Debug invoices are rarely used nowadays, but keep asking for maintenance
every time refactoring in primarily the invoice registry occurs. We have
passed the cost/benefit tipping point, so therefore the debug invoice
concept is removed in this commit.

Previously the debughtlc flag also controlled whether hodl masks were
active. It is safe to remove that additional condition because the hodl
masks are still guarded by the dev build tag.

lntest/itest/lnd_test.go

@@ -2372,10 +2372,7 @@ func testChannelUnsettledBalance(net *lntest.NetworkHarness, t *harnessTest) {
 	ctxb := context.Background()
 
 	// Create carol in hodl mode.
-	carol, err := net.NewNode("Carol", []string{
-		"--debughtlc",
-		"--hodl.exit-settle",
-	})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -2642,7 +2639,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Since we'd like to test failure scenarios with outstanding htlcs,
 	// we'll introduce another node into our test network: Carol.
-	carol, err := net.NewNode("Carol", []string{"--debughtlc", "--hodl.exit-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -3420,7 +3417,7 @@ func testSphinxReplayPersistence(net *lntest.NetworkHarness, t *harnessTest) {
 	chanAmt := btcutil.Amount(100000)
 
 	// First, we'll create Dave, the receiver, and start him in hodl mode.
-	dave, err := net.NewNode("Dave", []string{"--debughtlc", "--hodl.exit-settle"})
+	dave, err := net.NewNode("Dave", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -6277,8 +6274,7 @@ func testFailingChannel(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// We'll introduce Carol, which will settle any incoming invoice with a
 	// totally unrelated preimage.
-	carol, err := net.NewNode("Carol",
-		[]string{"--debughtlc", "--hodl.bogus-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.bogus-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -6740,7 +6736,7 @@ func testRevokedCloseRetribution(net *lntest.NetworkHarness, t *harnessTest) {
 	// protection logic automatically.
 	carol, err := net.NewNode(
 		"Carol",
-		[]string{"--debughtlc", "--hodl.exit-settle", "--nolisten"},
+		[]string{"--hodl.exit-settle", "--nolisten"},
 	)
 	if err != nil {
 		t.Fatalf("unable to create new carol node: %v", err)
@@ -6992,7 +6988,7 @@ func testRevokedCloseRetributionZeroValueRemoteOutput(net *lntest.NetworkHarness
 
 	// Since we'd like to test some multi-hop failure scenarios, we'll
 	// introduce another node into our test network: Carol.
-	carol, err := net.NewNode("Carol", []string{"--debughtlc", "--hodl.exit-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -7003,7 +6999,7 @@ func testRevokedCloseRetributionZeroValueRemoteOutput(net *lntest.NetworkHarness
 	// protection logic automatically.
 	dave, err := net.NewNode(
 		"Dave",
-		[]string{"--debughtlc", "--hodl.exit-settle", "--nolisten"},
+		[]string{"--hodl.exit-settle", "--nolisten"},
 	)
 	if err != nil {
 		t.Fatalf("unable to create new node: %v", err)
@@ -7240,7 +7236,7 @@ func testRevokedCloseRetributionRemoteHodl(net *lntest.NetworkHarness,
 	// Since this test will result in the counterparty being left in a
 	// weird state, we will introduce another node into our test network:
 	// Carol.
-	carol, err := net.NewNode("Carol", []string{"--debughtlc", "--hodl.exit-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -7253,7 +7249,7 @@ func testRevokedCloseRetributionRemoteHodl(net *lntest.NetworkHarness,
 	// trigger the channel data protection logic automatically.
 	dave, err := net.NewNode(
 		"Dave",
-		[]string{"--debughtlc", "--hodl.exit-settle", "--nolisten"},
+		[]string{"--hodl.exit-settle", "--nolisten"},
 	)
 	if err != nil {
 		t.Fatalf("unable to create new dave node: %v", err)
@@ -7657,9 +7653,7 @@ func testRevokedCloseRetributionAltruistWatchtower(net *lntest.NetworkHarness,
 
 	// Since we'd like to test some multi-hop failure scenarios, we'll
 	// introduce another node into our test network: Carol.
-	carol, err := net.NewNode("Carol", []string{
-		"--debughtlc", "--hodl.exit-settle",
-	})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -9854,7 +9848,7 @@ func createThreeHopNetwork(t *harnessTest, net *lntest.NetworkHarness,
 	// Next, we'll create a new node "carol" and have Bob connect to her. If
 	// the carolHodl flag is set, we'll make carol always hold onto the
 	// HTLC, this way it'll force Bob to go to chain to resolve the HTLC.
-	carolFlags := []string{"--debughtlc"}
+	carolFlags := []string{}
 	if carolHodl {
 		carolFlags = append(carolFlags, "--hodl.exit-settle")
 	}
@@ -10694,7 +10688,7 @@ func testSwitchCircuitPersistence(net *lntest.NetworkHarness, t *harnessTest) {
 	// Next, we'll create Carol and establish a channel to from her to
 	// Dave. Carol is started in htlchodl mode so that we can disconnect the
 	// intermediary hops before starting the settle.
-	carol, err := net.NewNode("Carol", []string{"--debughtlc", "--hodl.exit-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -11017,7 +11011,7 @@ func testSwitchOfflineDelivery(net *lntest.NetworkHarness, t *harnessTest) {
 	// Next, we'll create Carol and establish a channel to from her to
 	// Dave. Carol is started in htlchodl mode so that we can disconnect the
 	// intermediary hops before starting the settle.
-	carol, err := net.NewNode("Carol", []string{"--debughtlc", "--hodl.exit-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -11348,7 +11342,7 @@ func testSwitchOfflineDeliveryPersistence(net *lntest.NetworkHarness, t *harness
 	// Next, we'll create Carol and establish a channel to from her to
 	// Dave. Carol is started in htlchodl mode so that we can disconnect the
 	// intermediary hops before starting the settle.
-	carol, err := net.NewNode("Carol", []string{"--debughtlc", "--hodl.exit-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}
@@ -11684,7 +11678,7 @@ func testSwitchOfflineDeliveryOutgoingOffline(
 	// Next, we'll create Carol and establish a channel to from her to
 	// Dave. Carol is started in htlchodl mode so that we can disconnect the
 	// intermediary hops before starting the settle.
-	carol, err := net.NewNode("Carol", []string{"--debughtlc", "--hodl.exit-settle"})
+	carol, err := net.NewNode("Carol", []string{"--hodl.exit-settle"})
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)
 	}