Filter out relays according to candidate new Fast and Guard cutoffs

Once we have onionperf results with CBT and guards, we should create a stem script that emits a list of fingerprints for relays with bandwidth below candidate thresholds for Fast and Guard thresholds.

With this fingerprint list, we can use https://gitlab.torproject.org/tpo/metrics/onionperf/-/issues/33260 to filter out any onionperf circuits that contain fingerprints that would no longer be Fast. Same for Guard.

This analysis will help us learn if we need to change the Fast and Guard flag cutoffs to get improved performance from the network.