geom: use single level based tree position representation
The geometry tree nodes contain a position element (pos) that identifies the spatial position of the node. At internal nodes this node position is the partial position of a point and may either be represented using the magnitude of the decoded points, or the magnitude of the current depth. The first form equates to: nextPos = curPos | (xyz << currentNodeSize) The second: nextPos = (curPos << 1) | xyz Where xyz represents a position bit from the coded occupancy. In order to use the first form to determine neighbour relationships, curPos must be shifted down to represent position within the current depth. This repeated shifting, along with the introduction of simultaneous quantised and unquantised positions becomes increasingly difficult to follow when adding non-cubic nodes (via OtQtBt). This commit switches the representation to the second form above, eliminating various shifted forms and duplicate state. A decoded positions is inverse quantised when reaching a leaf node.