Add "--pool" and "--duration" flags to daemon CLI tools

Summary: Ref T12331. These changes are intended to make it easier to debug T12331 since I'm having difficulty reproducing the issue locally.

Test Plan:

• Ran bin/phd debug task --pool 4 and got an autoscaling pool.
• Ran bin/worker flood --duration 3 and got some 3-second-long tasks to execute with bin/worker execute ....

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12331

Differential Revision: https://secure.phabricator.com/D17431