Implement day view event clustering so that overlapping events can share latitude
Summary: Ref T4393, Implement day view event clustering so that overlapping events can share latitude.
Test Plan: Open day view in Calendar search query on a day with overlapping events. Overlapping events should be displayed side by side when possible, and should be layed out as a staircase when overlapping times.
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T4393
Differential Revision: https://secure.phabricator.com/D12711