o Major features (Proposal 332, onion services, guard selection algorithm):
    - Clients and onion services now choose four long-lived "layer 2" guard
      relays for use as the middle hop in all onion circuits.  These relays are
      kept in place for a randomized duration averaging 1 week each. This
      mitigates guard discovery attacks against clients and short-lived onion
      services such as OnionShare. Long-lived onion services that need high
      security should still use the Vanguards addon
      (https://github.com/mikeperry-tor/vanguards). Closes ticket 40363;
      implements proposal 333.