Better IME transition while switching app with recents (5/N)

With CL[1], the IME surface will have snapshot when transtioning to the
next task.
 
We can now remove the previous hacky logics like dedicates to keep the
previous IME and make the true IME target while task transitioning.
And, move the call of updateImeParent() from
DC#setInputMethodTarget to DC#updateImeControlTarget,
 
to ensure that the reparenting of IME insets source control can be done
when the IME insets visiblity settled down after the IME insets control
changed, to prevent unnecessary flickering during the time period between
reparenting IME parent and start IME insets animation.

Also, modify UpdateInputForAllWindowsConsumer#accept to let
mRecentsAnimationInputConsumer can be above IME target activity which to
prevent mis-touch or keystoke may left while quickly taping
soft-keyboard during swping up to recents.

[1]: I6bef36c779a28777408576f57e5d1c67d5d48e3f
 
Bug: 166736352
Bug: 153145997
Bug: 172815805
Bug: 174222049
Bug: 167604724

Test: manual as below steps:
   0) Device with 2-buttons or 3-buttons navbar mode.
   1) Launching an app with focusing an editor to show soft-keyboard.
   2) Pressing home key and observe if the IME screenshot exists during
      closing activity transition.
Test: manual as below steps:
   1) Launching an app with focusing an editor to show soft-keyboard.
   2) Tap IME settings icon to launch IME settings from Gboard.
   3) Observe if IME screenshot exists or soft-keyboard hided on the closing
      activity during transiting to IME settings.
   4) Press back key or swipe back to app task, observe if the keyboard
      showing animation occurs on the app task without janking.
Test manual as below steps:
   1) Launching an app with focusing an editor to show soft-keyboard.
   2) Swiping this app task to recents
   3) Quickly touch keyboard when leaving the finger from the screen.
   4) Expect there is no keystroke left or see the mistouch in keyboard
      while the task view into recents.

Change-Id: Ia6722e1cbccd7adc8aed1828265f6fa4df78df63