Refactor Ch-4_Ex-4.2 through to Ch-4_Ex-4.6 (inclusively) to utilise new Graph util

[Braden1996]

These exercises were completed using the (now deprecated) AdjacencyList util

Cracking-the-Coding-Interview-TypeScript/src/utils/AdjacencyList.ts

Line 6 in 78aa4ef

export class Node<T> {

They should be refactored to use the new Graph util:

Cracking-the-Coding-Interview-TypeScript/src/utils/Graph/index.ts

Line 6 in 78aa4ef

export default class Graph<T> {