Use a separate step for pypi upload

[blink1073]

The author of gh-action-pypi-publish does not intend to support nested usage of the action, so we'll have to switch to something manual. pypa/gh-action-pypi-publish#290. We have a script in drivers-evergreen-tools that we can copy from.

[blink1073]

Actually, a better approach is to do as they recommend and make it a top level action. I think we should wait until pypa/gh-action-pypi-publish#288 lands, and remove GitHub Attestations and PyPI publishing.