Summary: Fixes T5271. This is mostly similar to normal tab panel JS, but I think we'll eventually do async rendering and/or saved tabs so it's reasonable to split it out.
Test Plan: Toggled tabs on a tab panel, saw tab selected state change.
Reviewers: btrahan, chad
Reviewed By: chad
Subscribers: epriestley
Maniphest Tasks: T5271
Differential Revision: https://secure.phabricator.com/D9478
