Description

Some refactor of the interaction base classes in the multisystem framework. The main purpose is to make the code easier to understand. Main changes:

1. moved all components of interaction_t to interaction_with_partner_t
2. renamed interaction_t to interaction_surrogate_t
3. renamed interaction_partner_t to interaction_t

The end result is an interaction_t class that includes all the components and an "empty" surrogate class used only to avoid circular dependencies.

Also added as much documentation as I could.

News snippet

Some refactor of the interaction base classes in the multisystem framework.

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.