blocked by #393 and #396 (so sad the cute "blocked by" interface cant pick prs). i want to do a patch version of the program and a major version of the cli before doing this. should also remove ProgramClient at the same time (edit: this isnt important atm it just affects cli), iirc we orignally pulled it in because it provided a single send_transaction() interface with execution and simulation backends, but we use RpcClient for this already because we need the simulation results