cfg: rename legacyprotocol to protocol

Since we are also going to use it for experimental new features.

lntest/itest/lnd_test.go

@@ -982,7 +982,7 @@ func (c commitType) String() string {
 func (c commitType) Args() []string {
 	switch c {
 	case commitTypeLegacy:
-		return []string{"--legacyprotocol.committweak"}
+		return []string{"--protocol.committweak"}
 	case commitTypeTweakless:
 		return []string{}
 	}
@@ -4247,7 +4247,7 @@ func testMultiHopPayments(net *lntest.NetworkHarness, t *harnessTest) {
 	//
 	// First, we'll create Dave and establish a channel to Alice. Dave will
 	// be running an older node that requires the legacy onion payload.
-	daveArgs := []string{"--legacyprotocol.onion"}
+	daveArgs := []string{"--protocol.legacyonion"}
 	dave, err := net.NewNode("Dave", daveArgs)
 	if err != nil {
 		t.Fatalf("unable to create new nodes: %v", err)