Draft: Port ion ion interaction to the new framework
Description
Port the ion-ion interaction to the new framework (as child of force_interaction_t), create interaction as self-interaction of ions_t (instead of through the interactions_factory), include logical flag to decide where the interaction is computed for the same system (self-interaction) or for different systems, and adapt the code accordingly so that the loop ranges are properly defined and there is no double counting.
Checklist
-
I have checked that my code follows the Octopus coding standards -
I have added tests for all the new features added in this request.