Move cancel/retry/free task queue actions to bin/worker

Summary:
Fixes T6702. Ref T3554. Currently, tasks can be cancelled, retried and freed from the web UI by any logged in user.

This isn't appreciably dangerous (I can't come up with a way that a user could do anything security-affecting), but I think I probably intended this to be admin-only, but these actions should move to the CLI anyway.

Move them to the CLI. Lay some groundwork for some future `bin/worker cancel --class SomeTaskClass`, but don't implement that yet.

Test Plan: Used `cancel`, `retry` and `free` from the CLI. Hit all the error/success states.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T3554, T6702

Differential Revision: https://secure.phabricator.com/D10939