fix: update countBitsFlip to use uint64_t for parameters and counter

[Rudra2637]

Description of Change

Updated the countBitsFlip function to improve type safety and correctness:

• Changed the input parameter from int64_t to uint64_t to ensure only non-negative numbers are allowed.
• Changed the internal counter variable count from int to uint64_t to match the return type and prevent any theoretical overflow.
• Maintains original functionality for normal inputs.

This ensures the function is consistent, safe, and fully aligned with the intended use of counting set bits in non-negative integers.

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Checklist

• Added description of change
• Added file name matches File name guidelines
• Added tests and example, test must pass
• Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
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Notes:
Improves type safety for countBitsFlip function without changing its behavior for normal inputs.