Garbage collect Drydock logs after 30 days

Summary:
Ref T9252. Drydock logs are almost exclusively useful as a diagnostic tool for debugging immediate problems, so GC them fairly aggressively.

(I expect 99% of the usefulness of these logs to be within the first 24 hours, basically "why isn't my thing working". I can't really think of any cases where having old logs would be useful.)

Test Plan:

• Ran GC, saw it hit the log table (with no effect).
• Changed TTL from 30 days to 30 seconds, ran GC, saw it wipe recent logs.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9252

Differential Revision: https://secure.phabricator.com/D14197