Namespace `dateCreated` in Maniphest query construction

Summary: Fixes T5661. We may now pick up a conflicting `dateCreated` field from an edge table join.

Test Plan: Ran a project + dateCreated filtering query, no longer got an exception.

Reviewers: btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T5661

Differential Revision: https://secure.phabricator.com/D9997