Make relays (and similar) fetch from directory mirrors

Non-directory mirrors, should fetch from directory mirrors on a client schedule.

• Make non-directory mirror relays (there won't be many of these after #12538 (moved)), fetch from directory mirrors. They should FetchDirInfoEarly 0, just like clients do.
• Make anything that isn't an authority, fallback directory mirror, or directory mirrors fetch from directory mirrors, FetchDirInfoEarly 0, just like clients do.
• Modify directory_should_fetch_from_authorities():
  • change !server_mode or !advertised_server_mode to server_mode and advertised_server_mode and make those servers fetch on a client-like schedule
  • make the default case 0