[DEV]: Remove friend access of gametracer::aggame to AGG game class #1033

This is a marker for an internal refactoring. The aggame class in gametracer is given friend access to the AGG class. Aside from generally wanting to avoid friend declarations, this is something of a logical inversion as the game classes shouldn't need to be aware at all of anything to do with equilibrium computation methods.

This declaration should be removed, replaced either with public API calls or moving relevant functionality out of the AGG class itself.