[DOC] Looking into automating boilerplate in pydocs

[cjnolet]

As we continue to beef up and build out pylibraft, @dantegd pointed out that there's some boilerplate stuff in the pydocs that we could start centralizing and consolidating to make it easier to manage (and remove the duplication). An approach like what's being done in cuml current could be useful here.

[benfred]

This is partially done by #987 with consolidating the handle parameter docstring