Upgrade benchmark to Python 3.15

[radarhere]

Now that Python 3.15 has been released, let's upgrade the benchmark tests to use the latest Python version.

[codspeed]

Merging this PR will degrade performance by 13.78%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 3 (👁 3) regressed benchmarks
✅ 637 untouched benchmarks
⏩ 338 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
👁	test_draw_lines_blend[1237x811-0]	1 ms	1.2 ms	-13.82%
👁	test_draw_lines_blend[1237x811-127]	1 ms	1.2 ms	-13.72%
👁	test_draw_lines_blend[1237x811-255]	1 ms	1.2 ms	-13.8%

---

_{Comparing radarhere:benchmark (f7af951) with main (12b65ab)}

Footnotes

1. 338 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩