Use an HTTPEngineExtension to implement "https.blindly-trust-domains" in Arcanist
Summary: Ref T10227. This converts weird hard-codey magic to the new HTTPEngineExtension.
Test Plan: See D16090.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10227
Differential Revision: https://secure.phabricator.com/D16091