Account for preempting events on the Phrequent list view
Summary: Fixes T5850. Also fixes some logic where the wrong preempting events could be attached during a bulk query.
Test Plan: Phrequent list now shows preemption-aware times.
Reviewers: hach-que, btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T5850
Differential Revision: https://secure.phabricator.com/D10223