fix(ci): fix bad use of poetry groups + update to Python 3.12 in publish CI

[cyclimse]

Summary

What's changed?

• Stop using "main" as the default group in the custom "setup-poetry" action

Why do we need this?

• Fix the CI, which is blocking the deployment of release v2.0.1

• I previously relied on a strange behavior, when parsing flags which were lists of strings, poetry would ignore if an element was empty. It now considers this a valid input, so when passing "--only main,", it identifies two groups, main and ``. The latter is not a valid group, so it fails.

• TBH I'm not sure why I chose this approach as opposed to just using --with, I think there was a specific case where we only needed a non-main dependency group, so I chose this.

How have you tested it?

• Can't be tested via the CI, but this fix is taken from: https://github.com/scaleway/dagster-scaleway/blob/main/.github/workflows/publish.yml

Checklist

• I have reviewed this myself
• There is a unit test covering every change in this PR
• I have updated the relevant documentation

Details

[norbjd]

LGTM, difficult to say if it will work without releasing, but since it's a copy of what's done on https://github.com/scaleway/dagster-scaleway, and since it already worked there (https://github.com/scaleway/dagster-scaleway/actions/runs/8813500431), I'd say it should work too 😅