Align real hotseat with taskbar hotseat during drag and drop

Remove hotseat space from workspace in DeviceProfile if
taskbar is present, and instantly swap between taskbar and
hotseat when entering SpringLoadedMode. To allow for an exact
handoff, we also scale up the TaskbarView such that its icons
match the hotseat icon size when on the home screen.

Note that this CL only supports dragging to the taskbar, not
out of it (which still triggers system drag and drop instead).

Test: In RTL and LTR, drag a workspace item and ensure hotseat
seamlessly swaps with the taskbar hotseat and allows drops.

Bug: 179886115
Bug: 171917176

Change-Id: Id6462075b9b0b66b06d51a78c9c0b3e11e83e84d