Moves the item, with its descendants, to index among the children of parent.
public void MoveTo(PdfOutlineItem? parent, int index)
The new parent item, or null for the top level of the outline.
The position among the new parent's children once the item has been taken out, from 0 to their number.
ISO 32000-2 §12.3.3, Tables 150 and 151. The item's old neighbours are linked to each other and its new ones to it, its
Parent names the new parent, and the Count entries of both ancestries are corrected. Every view sees the move:
this item's and its descendants' Parent and Level, and both parents' Children.