Hover events should react to map movement

mapbox-gl-js version: v0.46.0-beta.1

Steps to Trigger Behavior

1. Set up a mouseenter/mouseleave listener on a layer.
2. Move the map by any means other than dragging (e.g. pan using keyboard, or programmatically zoom in on click).

Link to Demonstration

https://www.mapbox.com/mapbox-gl-js/example/hover-styles/
Click on the map to focus on it, then hover on a state and press a keyboard arrow to pan away. The hovered status doesn't change.

Expected Behavior

The mouse events should trigger when the map moves under the cursor just like they do when the cursor moves over the map.

Actual Behavior

The mouse events don't trigger on map movement.

Discovered this while setting up a "Click on cluster to zoom in and expand it" demo. It's pretty common to have "click on a feature to zoom in / center on it" interaction, but if you have hover states at the same time, they become glitchy.

cc @jfirebaugh

Start with the layer mouseenter/mouseleave listeners and the map movement behavior described in the reproduction steps. Reproduce the hover-styles example, then compare cursor movement with keyboard or programmatic map movement; done means hover events update when features move under the cursor.