Performance: replace custom sort by native sort

[bmesuere]

This pull request replaces the custom sort in utils.py by the built-in sort with cmp_to_key. There's a slight difference in output: the new version is stable whereas the original was not. All tests still pass.

In addition, I fixed a small bug in order fallback.

Performance of the function itself is ~50% better. When profiling the function in an actual exercise, the improvement was closer to 30%. Probably because it is then often called on (very) small lists. For exercises using sets, the impact is more noticable.

Next to the performance benefic, this simplifies the code.

[Copilot]

Pull request overview

This pull request refactors the sorted_no_duplicates function in utils.py to use Python's native sorted() function with cmp_to_key instead of a custom TimSort implementation. The change delivers ~30-50% performance improvement while simplifying the code significantly. The PR also fixes a bug in the TypeError fallback path where a boolean was incorrectly returned instead of an integer comparison result.

Changes:

• Replaced custom TimSort/insertion sort implementation with Python's built-in sorted() using cmp_to_key
• Fixed TypeError fallback in the order() function to return proper comparison integers instead of boolean
• Simplified duplicate filtering logic to be more straightforward

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