Only hide ime leash for invisible ime control target

In case the ime target is still on screen after swiping to home.
Such as a top floating window with a text input field.

Bug: 335204769
Test: Returns from landscape app to portrait home by gesture
      while an overlay floating window is the ime target. The ime
      should still be visible after returning to home.
Change-Id: Ib653b6160d4c4dac7dc17f1b8298a0c3e5f2252f