fix: update release workflow to publish to PyPI in the same workflow instead of workflow call

[dannycjones]

Which issue does this PR close?

• Closes fix release pyiceberg-core to pypi #2361.

What changes are included in this PR?

This change moves PyPI publishing into the publish.yml top-level workflow. The original Python release workflow instead is used for packaging only, and the artifacts are downloaded and published by publish.yml.

The existing workarounds are maintained for now, where committers can manually invoke the workflow to publish Python package artifacts.

In order to use this change, we must allow PyPI to additionally authenticate with `publish.yml. Instructions on how to add new publishers: https://docs.pypi.org/trusted-publishers/adding-a-publisher/

Are these changes tested?

No. I did not find a good way to dry-run test the workflow, so I do not have any PyPI equivalent to this: #2705

[dannycjones]

FYI @kevinjqliu @CTTY I'm hoping this is a mid-term fix for the PyPI trusted publishing. We're unblocked for 0.10.0-rc1 but for later releases, I'm hoping this simplifies things.

If not, I think we need an update to the release guide to specifically call out the need for manual workflow dispatch to complete the PyPI RC publish.