I've asked this on rl-list and got lots of interesting references to research papers.
So far the most promising one I've seen is this:
Nicolas Anastassacos, Stephen Hailes and Mirco Musolesi. Partner Selection for the Emergence of Cooperation in Multi-Agent Systems using Reinforcement Learning. In AAAI 2020. New York City, NY, USA. February 2020.
Your statement that researchers build their network from the ground-up using C++ or some other low level library couldn't be further from the truth.
You could take a look at this analysis showing the popularity of these two frameworks in the top ML conferences. The following Figure is taken from there.
In CVPR-2020, for example, TensorFlow and pytorch ...