Really all I needed for fixing the inheritance was _ssl._SSLContext.
But then I needed all the other stuff in _ssl, and if I was doing that
I wanted to do a thorough job of it.
Motivation was originally related to https://github.com/python/typeshed/issues/3968 ,
but we're well beyond that now, really.
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
