lnrpc: add XFindBaseLocalChanAlias rpc

Add the new RPC method that looks up the base scid for a given alias.
Given the previous stepping stones this commit is fairly simple, we just
call into the alias manager and return the lookup result.

lnrpc/routerrpc/router.pb.json.go

@@ -597,4 +597,29 @@ func RegisterRouterJSONCallbacks(registry map[string]func(ctx context.Context,
 		}
 		callback(string(respBytes), nil)
 	}
+
+	registry["routerrpc.Router.XFindBaseLocalChanAlias"] = func(ctx context.Context,
+		conn *grpc.ClientConn, reqJSON string, callback func(string, error)) {
+
+		req := &FindBaseAliasRequest{}
+		err := marshaler.Unmarshal([]byte(reqJSON), req)
+		if err != nil {
+			callback("", err)
+			return
+		}
+
+		client := NewRouterClient(conn)
+		resp, err := client.XFindBaseLocalChanAlias(ctx, req)
+		if err != nil {
+			callback("", err)
+			return
+		}
+
+		respBytes, err := marshaler.Marshal(resp)
+		if err != nil {
+			callback("", err)
+			return
+		}
+		callback(string(respBytes), nil)
+	}
 }