Adds westworld logging events for drag and drop on target bar buttons.

This would add below set of LauncherEvents:
* LAUNCHER_ITEM_DROPPED_ON_REMOVE
* LAUNCHER_ITEM_DROPPED_ON_CANCEL
* LAUNCHER_ITEM_DROPPED_ON_DONT_SUGGEST
* LAUNCHER_ITEM_DROPPED_ON_UNINSTALL
* LAUNCHER_ITEM_UNINSTALL_COMPLETED
* LAUNCHER_ITEM_UNINSTALL_CANCELLED

Sample Logs: https://docs.google.com/document/d/1CBP2yTcXdFhPdNG5ZmWFKSgd8mDbMevY-akVlUXPLDo/edit#bookmark=id.3ndtl1dalhdt

Bug: 152978018
Change-Id: I055a1b001524753eea71384b4765522f5946fbbc