Upgrade for Sopel 8, Python 3.8 to 3.12, and make it an entrypoint plugin

[Exirel]

This is a pretty significant change:

• renamed the Python package from sopel_module.imdb to sopel-imdb (this may need a migration guide)
• replaced setup.py and friends by pyproject.toml
• supported Python versions are now 3.8 to 3.12
• Sopel 8 or greater is required
• replaced sopel.module by sopel.plugin and other deprecation warning fix
• other minor packaging fixes

[Exirel]

Example of output with a fresh Sopel 8 install (and a properly setup api key):

12:07:27 <@xrl> .imdb Furiosa
12:07:27 <Sopel> [Movie] Title: Furiosa: A Mad Max Saga | Year: 2024 | Rating: 7.9 | Genre: Action, Adventure, Sci-Fi | Plot: The origin story of renegade warrior Furiosa before her encounter and teamup with Mad Max. | IMDB Link: http://imdb.com/title/tt12037194
12:07:57 <@xrl> https://www.imdb.com/title/tt1684562/?ref_=nv_sr_srsg_0_tt_7_nm_1_q_the%2520fall%2520g
12:07:58 <Sopel> [Movie] Title: The Fall Guy | Year: 2024 | Rating: 7.3 | Tomatometer: 89% | Genre: Action, Comedy, Drama | Plot: A down-and-out stuntman must find the missing star of his ex-girlfriend's blockbuster film.
12:11:33 <@xrl> .version imdb
12:11:33 <Sopel> [version] imdb v1.3.0.dev0

[dgw]

• renamed the Python package from sopel_module.imdb to sopel-imdb (this may need a migration guide)

Renaming other plugins from sopel_modules.name to sopel-name has been handled by publishing a new dummy version of sopel_modules.name that requires sopel-name, but that isn't necessarily the "best" approach. It will give users the newer package whenever they check for updates with pip install -U or whatever, but I haven't tested all the possible edge cases.

A lighter-weight alternative is to publish a new version (or just a post-release) of sopel_modules.imdb that updates its description (README) with a note that that version isn't maintained any more, and a link to the new package. You can see this approach with https://pypi.org/project/sopel-modules.youtube/0.5.2/ and its corresponding namespace-eol branch.

@RustyBower Does the publishing workflow here have a PyPI token that can create new projects? I would honestly recommend setting up Trusted Publishing for the new sopel-imdb package name, and I can help with that if you want. I've done it for about a dozen other packages now. 😁