Utilize PhutilMethodNotImplementedException

Summary: Depends on D9992. Utilize the PhutilMethodNotImplementedException class.

Test Plan: N/A

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10000