[Redesign] PHUIHeaderView goes to table layout

Summary: Ref T8099. This changes makes flexible layouts easier, and aligns icons, buttons better vertically.

Test Plan: Test various header locations, Phriction, Conpherence, Dashboards, Workboards etc.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D12961