Fix a NullPointerException caused by NEW_INSETS_MODE_FULL

InsetsSourceProvider.updateControlForTarget must be called while mWin
has the SurfaceControl. Otherwise, mAdapter will be cleared by
ControlAdapter.onAnimationCancelled. See
SurfaceAnimator.startAnimation.

This CL separates DisplayPolicy.prepareAddWindowLw into two parts:
1. Check if we can add a window to the system.
2. Apply policies on certain types of window.
We move the second part below mToken.addWindow. So the window has the
SurfaceControl while we set insets provider.

Bug: 118118435
Test: atest DisplayPolicyInsetsTests DisplayPolicyLayoutTests
Test: See if the system can be rebooted after entering the commands:
      adb root
      adb setprop persist.wm.new_insets 2
      adb reboot

Change-Id: I15c9a3ab49dee1c0f7009334adbd6fd1af8e0ba7