Garbage collect TTL'd cache entries from the general cache
Summary: We currently garbage collect general cache entries after a set period of time (30 days by default), but the recent changes to DarkConsole have left us writing a lot of large, short-TTL data to the cache. In addition to a maximum age, GC cache entires after they TTL out.
Test Plan: Ran GC daemon, saw TTL'd entries get collected. Inserted a TTL'd entry, saw it get collected by GC. Saw non-ttl'd entries not get collected.
Reviewers: chad
Reviewed By: chad
CC: aran
Differential Revision: https://secure.phabricator.com/D4990