Reparent IME window and handle non-fullscreen windows correctly

IME window is attached to the IME target if possible. This ensures
a smooth enter/exit animation when the activity is coming in/going
away.

Furthermore, if the controlling window doesn't span the entire
display, we can't offer controlling it in a frame-by-frame
manner, and we need to do the inset calculations relative to the
display frame.

Test:
adb shell setprop persist.wm.new_insets 1
adb shell setprop persist.pre_render_ime_views 0

Test: Open IME, go home, reopen app
Test: Show dialog with EditText
Bug: 111084606
Change-Id: Id40470f6f8284b48acfa4719049afd14fde332d6