Refactor most uses of AphrontFormDateControl to user AphrontFormDateControlValue

Summary: Ref T8024, Refactor most uses of AphrontFormDateControl to user AphrontFormDateControlValue

Test Plan: Countdown and Phrequent should now save form data in error state.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8024

Differential Revision: https://secure.phabricator.com/D12731