Adds LAUNCHER_FOLDER_LABEL_CHANGED event.

Sample Log: https://docs.google.com/document/d/1CBP2yTcXdFhPdNG5ZmWFKSgd8mDbMevY-akVlUXPLDo/edit#bookmark=id.qwjknn6acmx6

Bug: 155410872
Bug: 152978018

Change-Id: Ib7641d3d42a3f4fd002d1dbb36dc4b9ea0f885fc
5 files changed