Make WindowContainer surfaces container layers by default.

WindowContainers surfaces will never have a buffer so change them to be
container layers to avoid confusion on the buffer count in
SurfaceFlinger.

Also restrict SurfaceControl Builder to set a single surface type to
avoid confusion.

Test: go/wm-smoke
Bug: 122561221
Change-Id: I26b5810675ef3a3cc1a33533b6afcb0d0489d5ba