Add support for a "containerPHID" in the worker queue

Summary:
Ref T13591. Worker queue tasks which affect commits currently (mostly) store the commit as an "objectPHID", but do not directly reference the repository the commit belongs to.

This can make certain operations (like "change the priority of all tasks affecting repository Y") more difficult than it needs to be.

Support a "containerPHID", similar to the field of the same name on builds, that can store a parent object like a repository and better support operations against subsets of tasks.

See also D11044 for the genesis of "objectPHID".

This depends on the introduction of storage patch phases (in D21529) so that earlier migrations which queue worker tasks don't try to insert this column before it actually exists.

Test Plan:

• Ran bin/storage upgrade.
• No callers yet, see further changes for usage.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13591

Differential Revision: https://secure.phabricator.com/D21531