Remove almost all instances of HeraldContentTypeConfig
Summary: Ref T2769. This cleans up almost every use of the HeraldContentTypeConfig class.
Test Plan: Viewed and edited Herald rules.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T2769
Differential Revision: https://secure.phabricator.com/D6662