Improvements of wilcoxon test - backwards compatability

Hi all,

I have opened a pull request that implements the points 1-4 raised in ENH: stats.wilcoxon: rewrite for speed and clarity; add PermutationMethod support by mdhaber · Pull Request #19770 · scipy/scipy · GitHub. Since there is a small impact on the output of the function, I wanted to ask for feedback on the PR to make sure that the changes can be seen as improvements / fixes. The rationale why no deprecation cycle might be needed is documented in the issue comment referenced above.

Please join the discussion in the PR if you are interested. Thanks!

Christoph