Don't attach ime to app if target bounds don't match ime container

- This adds flexibility for AAOS where the apps will be running in
  DisplayAreas which have FULLSCREEN_WINDOWING_MODE but are not
  visually fullscreen.
- In such cases, the IME currently reparents to app surface by default.
- Having it reparent to the placeholder gives these benefits:
    a. Ensures that IME actually shows up if the DA is lets say on
       bottom half of screen
    b. Gives more flexibility for OEMs to control where the IME should
       go.

Fix: 344234345
Test: atest DisplayContentTests
Change-Id: Ifa6896b5dda073c02bac8d03538f2024b468469e