Investigate onionperf performance drop and how it relates to removing bad relays from the network

We seem to have a performance drop for onionperf measurements in Q2 2021 compared to Q4 2021. One hypothesis we had was that removing a bunch of bad relays from the network in Q1 could be the reason for that. We should investigate whether that's the case.

Getting this on @acute's @gaba's, and @mikeperry's radar.