[akshitam18]

Description of Change

Implemented Multilevel Feedback Queue (MLFQ) CPU scheduling in cpu_scheduling_algorithms/mlfq_scheduling.cpp.

• Added three scheduling queues: Q0 and Q1 use Round Robin with time quanta of 4 and 8, respectively, while Q2 uses FCFS.
• Processes are demoted when they exhaust their time quantum.
• Higher-priority arrivals can preempt lower-priority processes, and interrupted processes retain their unused quantum.
• Added seven test cases covering simultaneous arrivals, preemption, empty input, CPU idle time, quantum boundaries, and preservation of input order.

Checklist

• Added description of change
• Added file name matches [File name guidelines](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/CONTRIBUTING.md#New-File-Name-guidelines)
• Added tests and example, test must pass
• Added documentation so that the program is self-explanatory and educational - [Doxygen guidelines](https://www.doxygen.nl/manual/docblocks.html)
• Relevant documentation/comments is changed or added
• PR title follows semantic [commit guidelines](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/CONTRIBUTING.md#Commit-Guidelines)
• Search previous suggestions before making a new one, as yours may be a duplicate.
• I acknowledge that all my contributions will be made under the project's license.

Notes: Added an MLFQ CPU scheduling implementation with three priority levels and test cases for important scheduling scenarios.