Remove loadMemberPHIDs from PhabricatorProject

Summary:
Ref T603. Move toward stamping out all the Project / ProjectProfile query irregularities with respect to policies.

• Fixes a bug with Asana publishing when the remote task is deleted.
• Fixes an issue with Herald commit rules.

Test Plan:

• Viewed projects;
• edited projects;
• added and removed members from projects;
• republished Asana-bridged feed stories about commits.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7251