Enforce that global locks have keys shorter than 64 characters

Summary:
Fixes T7484. There's a bunch of spooky mystery here but the current behavior can probably cause problems in at least some situations.

Also moves a couple callsigns to monograms (see T4245).

Test Plan:

• Faked a short lock length to hit the exception.
• Updated normally.
• Grepped for other use sites, none seemed suspicious or likely to overflow the lock length.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7484

Differential Revision: https://secure.phabricator.com/D12263