Restructure cache checks to improve modularity
Summary:
Ref T5501. This code was headed down a bad road; dump an indirection layer between rendering and data gatehring.
In particular, this will make it much easier to lift these issues into setup warnings eventually.
Test Plan: Viewed cache status page.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T5501
Differential Revision: https://secure.phabricator.com/D12315