Add PhabricatorOwnersPackageQuery

Summary:
This is a step toward unearthing Project queries enough that I can make them policy-aware. Right now, some ProjectQuery callsites do not have reasonable access to the viewer. In particular, Owners packages need to issue Project queries because we allow projects to own packages and resolve project members inside of some package queries.

Currently, we have a very unmodern approach to querying packages, with a large number of one-off static load methods:

PhabricatorOwnersPackage::loadAffectedPackages()
PhabricatorOwnersPackage::loadOwningPackages()
PhabricatorOwnersPackage::loadPackagesForPaths()
PhabricatorOwnersOwner::loadAllForPackages()
PhabricatorOwnersOwner::loadAffiliatedUserPHIDs()
PhabricatorOwnersOwner::loadAffiliatedPackages()
ConduitAPI_owners_query_Method::queryAll()
ConduitAPI_owners_query_Method::queryByOwner()
ConduitAPI_owners_query_Method::queryByAffiliatedUser()
ConduitAPI_owners_query_Method::queryByPath()

We should replace PhabricatorOwnersOwner with an Edge and move all of these calls to a Query class. I'm going to try to do as little of this work as I can for now since I'm much more interested in getting a functional policy implementation into other applications, but ProjectQuery needs to be policy-aware before I can do that and I need to dig some at least some of the callsites out enough that I can get a viewer in there without making the code worse than it is.

This adds a PhabricatorOwnersPackageQuery class and removes one callsite of one of those static methods.

I also intend to dissolve the two separate concepts of an "owner" (direct owner) and an "affiliated user" (indirect owner via project membership) since I think we're always fine with "affiliated users" owners.

Test Plan: Loaded home page / audit tool, which use the modified path. Ran queries manually via script. Made sure results included directly owned packages and packages owned through project membership.

Reviewers: vrana, btrahan, meitros

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D3193