HiddenServicePort should connect to localhost by default

HiddenServicePort currently connects to 127.0.0.1 by default, but this will fail in configs where localhost is somewhere else in 127.0.0.0/8 or is [::1]. (Such as BSD jails.)

Instead, we can:

resolve "localhost", and check that it's in 127.0.0.0/8 or [::1], and use the IPv4 address first for compatibility with existing configurations
default to 127.0.0.1 if that exists
default to [::1] if 127.0.0.1 does not exist

This is not a security issue, as it results in a failed hidden service connection on unusual configs. It's a minor usability issue.

(Split from legacy/trac#17901 (moved) / legacy/trac#11360 (moved).)

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