Update reordering method names, and make 3d reordering API public

IsContainedVolume -> hasIsolatedZVolume conveys that this affects Z
ordering of views

ProjectToContainedBackground -> ProjectBackwards, since it ended up
using its own projection target, separate from the 3d volume bit

Change-Id: Ia2cde838cc4da134366fe6ff623290fbd65e50c3