Have forAllWindows return IME windows in order with IME target

If there is an IME target make sure to return the IME windows next
to the IME target when processing WindowContainer.forAllWindows().
Several users of forAllWindows are expecting this to be the cases so
it is close to the visual order.

Test: bit FrameworksServicesTests:com.android.server.wm.DisplayContentTests
Test: bit FrameworksServicesTests:com.android.server.wm.WindowLayersControllerTests
Change-Id: I737f88ca607ab2694391419d0d38060c03b53840