Humanize worker activity stats
Refs https://gitlab.com/teklia/requests/-/issues/870
Using a library like moment, we should be able to parse the Python timedeltas produced by CorpusWorkerActivity & ProcessWorkerActivity, and humanize them:
- from 00:00:03.327987 to 3.3 seconds
- frmo 01:00:10.412465 to 1 hour and 10 seconds