R1:2d7922908343

Modernize FeedQuery a little bit

Summary: Ref T12762. Updates some conventions and methods. This has no (meaningful) behavioral changes.

Test Plan:
- Grepped for `setFilterPHIDs()`.
- Viewed main feed, user feed, project feed.
- Called `feed.query`.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12762

Differential Revision: https://secure.phabricator.com/D18027