Route attached objects through new editor

Summary: Ref T2217. Nothing too surprising here. This transaction type is weird and should be replaced with the mainstream EDGE type at some point after things clear up more.

Test Plan: Attached and detached revisions and mocks.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2217

Differential Revision: https://secure.phabricator.com/D7085