Make it easier to retry in upload-pypi script

Recently the misc/upload-pypi.py script failed several times while I was uploading a release. It succeeded in uploading some wheels, but it failed at some point. It's possible to run it multiple times to work around the issue, but this is not ideal since it repeats all the work. Here some ideas about how to make this better:

• If upload fails, ask if the user wants to try uploading again. This would help by not having to download the wheels again.
• If upload fails, ask if the user wants to try uploading again, but only upload the wheels which haven't been successfully uploaded so far.
• Automatically retry, without asking for the pypi token/secret again.

Any of these would be an improvement over the current situation, but the first option might not help much if the script will just repeatedly fail at some point.

Beginne mit misc/upload-pypi.py und verfolge, wie das Skript Wheels hochlädt, Fehler behandelt und das PyPI-Token erhält. Kläre mit den Maintainer:innen, welches Wiederholungsverhalten implementiert werden soll; die fertige Lösung sollte es ermöglichen, dass eine fehlgeschlagene Veröffentlichung fortgesetzt wird, ohne erfolgreiche Arbeit zu wiederholen oder unnötigerweise erneut Zugangsdaten anzufordern.