Bandwidth utilization experiment

[evan-forbes]

We're needing a few features but need to do more investigating to determine which approach we should take. More info in the tracking issue

We want to be able to measure bandwidth utilization over a realistic geographically distributed network using different stacks such as TCP+BBR and QUIC. To close this issue, we should report the bandwidth utilized by a very simple reactor that only sends bytes for each stack. such a branch can be found on this branch. The bandwidth should be measured "back to back", meaning the same exact set of nodes and connections should be used to ensure that the comparisions are meaningful.