Have WM use token info. from IMMS to determine IME target window

Window Manager currently places the IME above the highest window
that can possibly be using the IME. While this method works for
most cases, it does cause some animation jank if the window making
the IME visible is below an other window that could possibly make
the IME visible, but isn't. When this happens the IME is displayed
on-top of which we don't want since the top app isn't making the
IME visible.
We now rely on a strong signal from the input method manager service
WMS.updateInputMethodWindowStatus() to depend which window is actually
using the IME so the window manager can z-order things correctly.

Fixes: 31559891
Test: bit FrameworksServicesTests:com.android.server.wm.DisplayContentTests
Change-Id: I524aa9dbeb764aac15034a13adf9381304c38fa6