Fix ActivityEmbedding Shell transition animation with reparent

With legacy transition, we capture a screenshot of the reparent child,
and attach it to the parent surface (in WM Core), and then animate the
parent in handler.

With Shell transition, we also need to do the same (in WM Shell) to
screenshot the reparent child, and animate the parent using the child's
change info. Otherwise the child animation will be cropped.

Bug: 207070762
Test: manual
Change-Id: I52b5c839343864b4179e5c35c33343bc282bc189