Add NIU Actions buttons to the Go Overview

The buttons send Intents to the designated app (specified by
niu_actions_package) to do the following:
Listen - Read the contents of the screen aloud
Translate - Translate the contents of the screen
Search - Perform a visual search on the contents of the screen

The Intents also include (via URI) the screenshot of current app used as
a thumbnail by Recents.

The feature is controlled by the enable_niu_actions flag, set to false
here. Both this flag and the niu_actions_package String must be set for
a given Launcher to use these buttons.

Bug: 177955244
Bug: 177955748
Test: Manual (enabled on LauncherGoGoogle and sent Intents to demo Lens
app)

Change-Id: I3d1f870bb176ed0cbae637a45c072bd8acac1d4b