Split PROXY errors into whatever reasons are given in TorCtl logs
If we combine TGen transfers with Tor streams and circuits we can learn a lot more about why our proxy (Tor) failed. Including that information in visualizations might be very useful.
When we match TGen transfers with TorCtl events, we'll have to look how metrics-lib does this.
Maybe we can use some ideas from legacy/trac#30612 (moved) where we discussed putting an error code graph on Tor Metrics.