R1:490a6fe8b1ac

[Redesign] Convert Dashboard Panels to ObjectBox

Summary: Moves Dashboard Panels to use PHUIObjectBoxView and PHUIHeaderView

Test Plan:
Tested the most common dashboards, Differential, Maniphest, Projects, Feed, Audit. Some edge cases (Legalpad, Macro) still are in progress. Tested laying out a new Dashboard, removing panels, moving panels.

{F406170}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.