Method mergeNodes

Function that merges two leaves together; in this case we must have two leaves, left and right that are merged and their parent that must be an internal node (or root). We also have the index of the parent that the pointers indicate these two leaves it should be like this: parent

(TreeLeaf left, TreeLeaf right, TreeLeaf other,
                            TreeInternalNode parent, int parentPointerIndex,
                            int parentKeyIndex, boolean isLeftOfNext,
                                boolean useNextPointer)