Add "--force" and "--quickly" flags to bin/lipsum

Summary:
Ref T12319.

• Lipsum can trash an install by creating a lot of junk that's hard to get rid of, so we're cautious about letting you run it. Add a --force flag if you're sure you know what you're doing. This makes the edit/test cycle a bit easier when actually writing Lipsum generators.
• Lipsum normally sleeps for a second before creating objects, to give users more control over how much stuff they create and limit the amount of damage caused by mistakes. Sometimes, you want to generate a LOT of stuff because you want to reproduce a performance/scale issue (like T12319). Add a --quickly flag to generate objects as fast as possible.
• When loading random users (used as authors, assignees, etc), also load user settings so we can ConduitCall with them.
• Allow generators to return a PHID instead of an actual object (more convenient for Conduit-based generators).

Test Plan:

• With next change, ran lipsum generate badges --force --quickly.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12319

Differential Revision: https://secure.phabricator.com/D17421