gh-136672: Docs: Move Enum functions and add examples

[RafaelWO]

When the Enum functions _add_alias_ and _add_value_alias_ were added in de6bca9, the documentation for them was done under EnumType instead of Enum.

This change moves them to the docs of the Enum class and adds an example for each function.

Additionally, it moves the versionadded for EnumType to the top and fixes the indentation of another versionchanged entry.

• Issue: Multiple issues with enum __add_(value_)alias_ documentation #136672

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📚 Documentation preview 📚: https://cpython-previews--136791.org.readthedocs.build/

[RafaelWO]

Thanks for reviewing, @AA-Turner 🙃

[ethanfurman]

Mostly good, just one small change.

[ethanfurman]

Please move these lines to the bottom of the list.

[RafaelWO]

Fixed!

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[AA-Turner]

Thank you @RafaelWO! Please could you have a look at Ethan's suggestions.

A

[RafaelWO]

Upon fixing the ordering of the methods under "Supported _sunder_ names", I noticed that this section and the above ("Supported __dunder__ names") are duplicated in the enum API docs and enum HOWTO - but they are not in sync.

Is there a way to connect those sections (i.e. include the content to have only one source of truth)? Or should I just remove one, e.g., in the HOWTO, and link to the other one?

Thanks for your suggestions!