Add support for offsetting the voting interval in order to bootstrap faster.
A new option TestingV3AuthVotingStartOffset is added which offsets the starting time of the voting interval. This is possible only when TestingTorNetwork is set. This patch makes run_scheduled_events() check for new consensus downloads every second when TestingTorNetwork, instead of every minute. This should be fine, see #8532 for reasoning. This patch also brings MIN_VOTE_SECONDS and MIN_DIST_SECONDS down from 20 to 2 seconds, unconditionally. This makes sanity checking of misconfiguration slightly less sane. Addresses #8532.