Change migrations to not rely on "arcanist project" classes

Summary: Ref T7604. Change two migrations to query arcanist project information using queryfx directly to avoid the need for the LiskDAO fields to exist.

Test Plan:
Ran the following commands to verify that things weren't majorly broken:

• ./bin/storage upgrade --apply phabricator:20150503.repositorysymbols.2.php
• ./bin/storage upgrade --no-quickstart --namespace test

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7604

Differential Revision: https://secure.phabricator.com/D13011