Consensus-health checker should warn if auths assign flags to unusually few or many relays
We should notice cases like #8683 (moved) much earlier by adding an alert to the consensus-health checker. It could simply compare the number of flags in a vote and in the consensus. If there are more than, say, 250 relays that have a certain flag only in a vote or only in the consensus, the consensus-health checker should emit a warning. See also the bottom of the consensus-health output page for recent numbers. Related to #8164 (moved).