In order to help debug networking-related problems, we now include log

timers around all outgoing requests to Celery. This includes task runs

and tool refreshes. These are DEBUG-logged unless timing exceeds a

threshold, helping to catch delayed requests.
As this utilizes new functionality in Djblets 5.3 / Review Board 7.0.1,

we're including a backport of the modern log_timed(). This will be

removed when we can depend on newer releases.

Tested worker status refreshes, tool refreshes, automatic tool runs,

and manual tool runs. All provided the correct logging information.
Unit tests pass.