tor/changes/ticket40652

  o Minor features (dirauth):
    - Add an AuthDirVoteGuard torrc option that can allow authorities to
      assign the Guard flag to the given fingerprints/country code/IPs. This
      is a needed feature mostly for defense purposes in case a DoS hits the
      network and relay start losing the Guard flags too fast.
    - Make UPTIME_TO_GUARANTEE_STABLE, MTBF_TO_GUARANTEE_STABLE,
      TIME_KNOWN_TO_GUARANTEE_FAMILIAR WFU_TO_GUARANTEE_GUARD tunable from
      torrc.
    - Add a torrc option to control the Guard flag bandwidth threshold
      percentile. Closes ticket 40652.