gh-138094: Fix misleading suggestions in interactive help prompt

[adqm]

This PR represents an attempt to address both of the issues raised in #138094 by changing how help(help) is handled, and by removing suggested calls to help(...) in the output when we can't find a given topic in interactive mode.

Happy to adjust if need be (or to separate this into 2 PR's if that would be better).

• Issue: help function: misleading output in interactive mode, confusing output for help(help) #138094

[ZeroIntensity]

I think it's worth adding an entry to the "What's New in Python 3.15" page too, because this seems like a feature, not a bugfix.

[adqm]

I think it's worth adding an entry to the "What's New in Python 3.15" page

I'm not sure, just because this PR alone represents pretty minor tweaks to help's behavior. But maybe in conjunction with #137966 if these both get merged in, it would make sense? I also have a few other ideas in mind so there may be additional help-related PR's coming when I have a chance.

Of course, happy to defer to y'all's judgment, though.

[ZeroIntensity]

Alternatively, we could add a .. versionchanged note to help, because this is a behavior change. #137966 should definitely get a whatsnew entry, though.