Revamp the Base Class for graph representation

[yashrsharma44]

Currently, we use the graph_base.js as a base class for Graph Objects. Different Algorithms use this class for creating a graph object using the public methods that we have currently. However, the internal implementation of graph methods is really obfuscated/complex, which makes it tough to understand and maintain.

Simplify the internal implementation of the graph object.

Before solving the issue, please discuss a small implementation approach before sending in a PR.