Added Observability features

[JotaDeRodriguez]

I propose adding these economic metrics to the negotiation environment so that we could study the turn by turn performance of both players as the game develops. This could be particularly important to provide a baseline and evaluate specialized models down the line.

Some of the key metrics are:

• The value for each player both in the offer and requests
• The amount of resources offered / requested
• whether or not the trades are valuable for one, both or neither player
• gains / losses for both players
• the value creation / value efficiency of the trade
• overall results of the game
• etc

Ideally a smarter / more capable model should be able to extract more value from less capable models. We could even set the models to find mutually beneficial solutions and use these metrics to ensure that the overall value for both players goes up.