Modularize config modules + add edges, phid modules

Summary: Fixes T6859. Adds a readout in /config/ of installed edge and PHID types. See also D13626.

Test Plan:

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T6859

Differential Revision: https://secure.phabricator.com/D13662