Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST.
According to the definition of LCA on Wikipedia: "The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself)."
[2, 10^5]-10^9 <= Node.val <= 10^9Node.val are uniquep != qp and q will exist in the BSTroot = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 86root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 42root = [2,1], p = 2, q = 12