[NODE][REFACTOR] Rename IRFunctor->NodeFunctor, use func pointer (#4247)

[NODE][REFACTOR] Rename IRFunctor->NodeFunctor, use func pointer (#4247)

* [NODE][REFACTOR] Rename IRFunctor->NodeFunctor, use function pointer for dispatching.

Previously we used std::function for the functor dispatching.
It introduces additional overhead and problems during dll destruction(of std::function).

This PR changes the std::function to function pointers.
This change a bit restrictions around the set_dispatch that we can get around,
but will improve the general efficiency by reducing one level of indirection in the std::function.
We also no longer need special marcos to register functions to the Functor.