Have the on_robot_built_tile event give the surface_index directly

[project6]

Yes, we can get the LuaSurface through the entity. But seeing as on_player_built_tile provides the surface_index it seems inconsistent. Having the surface_index given seems relevant since acting the built tiles requires it.

[bobingabout]

I'd guess that if it was on the player version but not the robot version, then it is likely something that was overlooked.