Common documentation/docstring related utlities

[Zethson]

Description of feature

I think quite many of our packages use a method to inject specific parameters into docstrings to DRY them. Maybe scverse-misc could provide general utilities for docstring handling or more broadly documentation.

We could discuss whether some of these should go into the upcoming scverse-doc (scanpy-doc) instead.

[flying-sheep]

Yeah, this is part of both deprecated and the upcoming settings.

Maybe it would be possible (and make sense) to have a sphinx extension here instead of modifying the docstrings. That way we could use introspection to implement the features, and if people want, they could choose to use something other than Sphinx.