Initiate Hotseat drag from long pressing corresponding Taskbar item

When you long press on the taskbar hotseat item, the following happens:
- We start a system drag and drop with an invisible drag shadow
- We create a new DragOptions with the simulatedDndStartPoint set to the
  drag down position, and tell Launcher to use that for the next drag
- We perform a long click on the equivalent Hotseat item in Launcher
- We pass the drag events of that operation to Launcher's DragController

This allows Launcher to handle the entire drag operation, including the
pre-drag (with popup), and taskbar already hides when the drag starts.

Test: Long press items in taskbar hotseat, able to drag them to workspace

Bug: 179886115
Bug: 171917176
Change-Id: I576b80cb1bd0225cdc91cf7689fdee0481265109