Count dists before uploading scientific wheels or publishing to PyPI

[hugovk]

Re-do of #139.

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Suggestions for python-pillow#9239

• Update actions/download-artifact to v5
• Count dists before uploading scientific wheels or publishing to PyPI. If we suddenly started producing more wheels than expected, maybe we should inspect that before sharing those wheels?
• At the moment, the printed number of dists and the number of dists checked by the condition are from two different ls operations. I suggest making that the same operation, so the user can be confident in what the output is saying.

[hugovk]

OK, this is looking better:

          - name: "iOS arm64 simulator"
            platform: ios
            os: macos-14

https://github.com/hugovk/Pillow/actions/runs/18427576368/workflow?pr=140#L101