Smooth out slide in/out animation for the overview panel

Change-Id: I742d2248b7cf70767f9e776d88db6fc1aaa767ce
Trebuchet: launch framework WallpaperPicker

After long pressing on the home screen and selecting "Wallpapers"
Trebuchet's activity was being called.

We have now switched to framework's WallpaperPicker activity, so open
that one instead.

Change-Id: I97165350f1b995ae921eebbc126eb3e0e2396963
Signed-off-by: Roman Birg <roman@cyngn.com>
Fixing issues introduced in 31cc95a0:
 - HotSeat needs go visible/invisible when transitioning in and out of overview mode
 - Animation listener for setting alphas needs to remove itself when the animation finishes

Change-Id: I654c0e700c9bc3f77692ed653f8158cec1f2430b
Fixes:
 - Hide search bar if live settings are toggled in overview mode
 - Restore workspace outlines in overview mode after live settings changes

Change-Id: Iee9894f674c78ba3c82486de97e34d610c04a2a5