BUG: ensure that docstrings for read/write public methods are always available for inspection (io.registry) (⏰ wait for #17559) - #17557

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looks like I made a mistake here. However, #17558 makes this extra difficult to debug, so I'm going to prioritize that issue before I come back here.

This now includes the patch from #17559 for convenience, but I still expect a merge conflict so I'll giving the other PR priority as it's also a backport candidate.

closing this following discussion over at #17555