Identify candidates for FallbackDir, and ship with a list of them
Back long ago, we added a feature to allow torrc to list a bunch of FallbackDir entries. These tell a client where to look for consensus directory documents, so that the clients don't just load the authorities down.
It would be good if we shipped with such a list.
One idea has been to identify directories that have:
- a stable IP:Port over a long time,
- reasonably good uptime (as a fraction)
- good bandwidth
- a contact address.
Then, contact the admins of these directory caches and ask them for permission to put them on a list.
(See also #8374 (moved))