Create and analyse dependency graph

[AlexandraVolokhova]

Observation: Currently there're no documented conventions on how different methods in different modules (environments, gflownet agent, policies, proxies) interact with each other and it makes it difficult to introduce changes in each of the module without breaking something in this interaction. It has been a source of bugs in the past multiple times.

Proposal: Let's create and analyse the graph of the existing dependencies, document it, and then look into how we may want to simplify it. I remember @josephdviviano generated such a graph sometime ago, maybe we could revive this effort and look into it together?