R1:f0db6e48189d

Migrate Project edges to subclass `PhabricatorEdgeType`

Summary: Modernize Project edges to subclass `PhabricatorEdgeType`. Largely based on D11045.

Test Plan: Add a member to a project, saw new rows in the `phabricator_project.edge` and `phabricator_user.edge` tables.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11111