R1:c0e20a11c1d4

Add a "projects" Search attachment for Conduit APIs

Summary: Ref T9964. Builds on D14772. Allows callers to request project PHIDs for objects.

Test Plan: {F1025468}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9964

Differential Revision: https://secure.phabricator.com/D14773