Replace secondary app windows across activity relaunch.

Windows of TYPE_APPLICATION (as opposed to TYPE_BASE_APPLICATION)
are not child windows in the sense of SurfaceView, etc, as they are
independent windows like Modal Dialogs rather than embedded parts
of other windows. Still though, we expect them to reappear following
activity relaunch, and they won't be covered by window preservation,
so we need to mark them for replacement.

Bug: 26668339
Change-Id: I652b4137085f6ef4d6c9d54de609727f966ef4d6