Add order-by-ID to PhabricatorWorkerTriggerQuery

Summary:
Ref T6881. By design, the EXECUTION order only selects tasks which have been scheduled (since it performs a JOIN). This is inconsistent with other queries and problematic for withID/withPHID queries which may want to select an unscheduled task.

Switch to standard ID ordering by default.

Test Plan:

• Instances console now finds unscheduled triggers.
• Verified that all existing queries specify an explicit order.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6881

Differential Revision: https://secure.phabricator.com/D11436