ci: update actions/(upload|download)-artifact

[agoose77]

This PR updates our various CI actions and reworks the packaging test workflow.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f6d6f5c) 81.98% compared to head (91cb713) 81.98%.

Additional details and impacted files

[jpivarski]

This looks like an upgrade to upload-artifact@v4 and changing some names. That's all good, though we'll need to change the set of required tests, which will affect everyone with an open PR.

So, it's not ready to merge until we coordinate with everyone who has an open PR.

(I'll be out of touch until Sunday.)

[agoose77]

I updated the branch status checks using

commit="<SOME-SHA-WITH-NEW-CHECKS>"
# Read checks
gh api repos/scikit-hep/awkward/commits/${commit}/check-runs --paginate --jq '{ context: .check_runs[].name }' | jq -s '{ checks: . | unique }' > /tmp/checks.json
# Remove the check pertaining to docs deployment (skipped for PRs)
$EDITOR /tmp/checks.json
# Patch checks
gh api repos/scikit-hep/awkward/branches/main/protection/required_status_checks \
  --method PATCH \
  --input /tmp/checks.json