Add Google Test (gtest) Unit Testing Framework

[priyanshscpp]

Description:

This issue proposes the integration of Google Test, a C++ testing framework, into the CPU-Scheduling-Algorithms project for systematic unit testing of each CPU scheduling algorithm implementation.

📌 What is the goal?

To set up Google Test to test the correctness and edge cases of all implemented scheduling algorithms:

FCFS (First Come First Serve)

RR (Round Robin with time quantum)

SPN (Shortest Process Next)

SRT (Shortest Remaining Time)