Implement LAUNCHER_ITEM_DRAG_STARTED event.

* Fixes null component issue when ItemInfo object copiedFrom.
* Fixes missing container when item is dragged from hybrid hotseat.

Sample Logs:
2020-04-30 14:09:45.499 30472-30472/com.google.android.apps.nexuslauncher D/StatsLogManager: LAUNCHER_ITEM_DRAG_STARTED
    # com.android.launcher3.logger.LauncherAtom$ItemInfo@260f31f8
    application {
      component_name: "com.android.chrome/com.google.android.apps.chrome.Main"
      package_name: "com.android.chrome"
    }
    container_info {
      workspace {
        grid_x: 2
        grid_y: 2
        page_index: 2
      }
    }
    is_work: false

2020-04-30 14:23:15.230 31320-31320/com.google.android.apps.nexuslauncher D/StatsLogManager: LAUNCHER_ITEM_DRAG_STARTED
    # com.android.launcher3.logger.LauncherAtom$ItemInfo@608f101
    application {
      component_name: "com.google.android.gm/.ConversationListActivityGmail"
      package_name: "com.google.android.gm"
    }
    container_info {
      hotseat {
        index: 1
      }
    }
    is_work: false

Bug: 152978018

Change-Id: I3d3ce213fd2fc6eb5ffb239e048ceb7c0fa88b53