Add a "lock log" for debugging where locks are being held

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