Destroy app-less surfaces when becoming invisible with no animation.

Otherwise there is no later point to destroy them and they linger
around indefinitely. tryStartExitingAnimation seems like a safe point
as we only call this from relayout and the client renderer is paused
at this point, as long as we ensure we don't return a surface (which we won't
since we have laid out to invisible) we should be assured that the client
will not try again to render.

Bug: 77911541
Test: Manual. Docked divider window is destroyed when dismissed.
Change-Id: I2ed37f460a7f258083ab1c196c4e5f7a35e3d557