R1:32c6b649dd21

Move Harbormaster log compression to the worker task queue

Summary: Depends on D19130. Ref T13088. Currently, when a build log is closed we compress it in the same process. Separate this out into a dedicated worker since the plan is to do a lot more work during finalization, none of which needs to happen inline during builds (or, particuarly, inline during a Conduit call for API writes in the future).

Test Plan: Ran `bin/harbormaster write-log --trace`, saw compression run inline.

Subscribers: PHID-OPKG…