[api] Reduce flash usage in user services by eliminating vector copy (#10971)

esphome/components/api/user_services.h

@@ -55,7 +55,7 @@ template<typename... Ts> class UserServiceBase : public UserServiceDescriptor {
 
  protected:
   virtual void execute(Ts... x) = 0;
-  template<int... S> void execute_(std::vector<ExecuteServiceArgument> args, seq<S...> type) {
+  template<int... S> void execute_(const std::vector<ExecuteServiceArgument> &args, seq<S...> type) {
     this->execute((get_execute_arg_value<Ts>(args[S]))...);
   }