[Redesign] People, Profile, Feed UI

Summary: Ref T8099, Mostly a Feed cleanup, removing old CSS, relying on modern display objects, adds back the feed to profile (I miss it, but maybe you don't).

Test Plan: Visit Feed on Profiles, Projects, Feed, and Dashboards. Same UI Everywhere. TODO, "Public Feed".

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13101