lnwallet: add anchor commitmenttype

With this commitment type, we'll add extra anchor outputs to the
commitment transaction if the anchor channel type is active.

lnwallet/transactions_test.go

@@ -1090,7 +1090,7 @@ func testSpendValidation(t *testing.T, tweakless bool) {
 	}
 	commitmentTx, err := CreateCommitTx(
 		channelType, *fakeFundingTxIn, keyRing, aliceChanCfg,
-		bobChanCfg, channelBalance, channelBalance,
+		bobChanCfg, channelBalance, channelBalance, 0,
 	)
 	if err != nil {
 		t.Fatalf("unable to create commitment transaction: %v", nil)