> Clinic should be adding 'self' to the signature,
> which should then be picked up by the __text_signature__
> parser, and used by inspect and pydoc.

This innocent little comment has derailed my whole day.  You're right, 'self' should be in the signature.  But not always!  And then in
inspect.Signature we need to strip it off for bound methods.

In case you're curious, this work is happening in a separate branch, and tracked in a different issue (#20189).