R1:9b0b50fbf469

Give "bin/worker" flags to repeat and retry tasks

Summary:
See PHI1063. See PHI1114. Ref T13253. Currently, you can't `bin/worker execute` an archived task and can't `bin/worker retry` a successful task.

Although it's good not to do these things by default (particularly, retrying a successful task will double its effects), there are plenty of cases where you want to re-run something for testing/development/debugging and don't care that the effect will repeat (you're in a dev environment, the effect…