Summary: Depends on D19173. Ref T13096. Adds an optional, disabled-by-default lock log to make it easier to figure out what is acquiring and holding locks.
Test Plan: Ran `bin/lock log --enable`, `--disable`, `--name`, etc. Saw sensible-looking output with log enabled and daemons restarted. Saw no additional output with log disabled and daemons restarted.
Maniphest Tasks: T13096
Differential Revision: https://secure.phabricator.com/D19174
