Call prepareSurfaces in applySurfacesChangesTransaction

Instead of doing custom magic by conditionally calling
prepareSurface but only on the WindowAnimator, we just prepare
all surfaces. This avoids issues with transaction position/size
caching as the cached size/position might not be applied early
enough/could be reordered.

Test: go/wm-smoke
Test: Enter split screen, resize things, ensure everything is
absolutely in sync.

Change-Id: I9ff5e6fd37dde9406b1529c86daf42061b282cb2