Make chutney check tor's logs for reachability self-test success
This ticket is an alternative to legacy/trac#33582 (moved) or legacy/trac#33222 (moved).
Instead of fixing bridge descriptor uploads, we can check bridge logs to make sure that reachability self-tests have succeeded.
For consistency, we should also do the same checks for relays.
We can only do these tests on authorities, relays, and bridges that are configured with AssumeReachable 0. Chutney's current defaults are:
- directory authorities: 1
- bridge authorities: 1
- relays: 0
- bridges: 0
- clients: clients never perform reachability self-tests
Some custom chutney networks may set AssumeReachable 1 for relays and bridges. So we should make it easy for them to disable these checks.