DOC: improve various docstrings

[OutSquareCapital]

• - PyoIterator methods who use builtins or rust Iterator methods -> add infos from their respective official doc
• - sorted collections as a whole, heapq, pyocounter, deque and sliceview who were "traduced" from their original impls, but are still not really aligned with desired style
• - fix as many issues as reasonnable flagged by doctest_checker
• - builtins wrappers, who could benefit, just like I did with PyoIterator, with added infos from python library
• - In general, correctly handle links between methods for website. This is far from done