CI: ensure we build properly tagged wheels

[robertlong13]

Alternative to #1038

• Builds wheels for all linux systems (and python versions 3.8+)
  • xml packages needed to be installed on Alpine (for musllinux i686)
  • We should build Mac and Windows wheels in a future PR so they can benefit from the speedup
• Double-check the existence of the wheels and copy them to the dist folder
• Build the sdist so pip can fall back to compiling it
• Upload artifacts so they can be checked and tested (I have not actually tested installing the wheels or the sdist, but I see no reason why they shouldn't work)