PERF: Cythonize kendall correlation

[Alvaro-Kothe]

• closes DataFrame.corr(method="kendall") calculation is slow #28329 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.
• I have reviewed and followed all the contribution guidelines
• If I used AI to develop this pull request, I prompted it to follow AGENTS.md.

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This implementation is mainly an adaptation of Julia's implementation.

Benchmark results

Change	Before [e49b4e0]	After [3cde96d] <perf/kendall>	Ratio	Benchmark (Parameter)
-	291M	234M	0.81	stat_ops.Correlation.peakmem_corr_wide('kendall')
-	46.8±2ms	10.9±1ms	0.23	stat_ops.Correlation.time_corr('kendall')
-	2.55±0.2s	372±5ms	0.15	stat_ops.Correlation.time_corr_wide_nans('kendall')
-	2.51±0.1s	352±4ms	0.14	stat_ops.Correlation.time_corr_wide('kendall')