Add basic stats to tasks
This just increments a counter for started tasks, ended tasks, tasks that failed with an exception. It also registers a timer for every task run.
The way the celery worker name is pulled is a bit hideous and there must be a better way, but I couldn't find one...
Test Plan
Need to figure out the proper way to inject a statsd in "unit" tests, but at least the Docker changes allow you to see what the data would look like.
Migrated from D1007 (view on Phabricator)