Hide tooltips on any keypress

Summary:
Fixes T4586, where a keystroke like "return" to submit a form could remove DOM nodes rendering a tooltip, leaving the user with a permanent phantom tooltip.

(@spicyj, if you come up with anything better than this feel free to send a followup, but I //think// this is a reasonable fix.)

A nice side effect of this is that it hides any tooltips obscuring a text input when you start typing.

Test Plan: Hovered over a tooltip, pressed a key, tip vanished.

Reviewers: spicyj, btrahan

Reviewed By: btrahan

Subscribers: aran, spicyj, epriestley

Maniphest Tasks: T4586

Differential Revision: https://secure.phabricator.com/D8497