Backport fixes, Use PEP 517 workflow, Use SPDX license, upgpkg 0.22, upgpkg 0.23

• Backport fixes for test failures.
  • https://github.com/hgrecco/pint/commit/1b2b0592f88a1c9fdf9b5649ebade19fa81adea4
  • https://github.com/hgrecco/pint/commit/833a5ca4dfb11eb3670c600b63ad67a061251d8a
  • https://github.com/hgrecco/pint/commit/b3b18277ecc682bff7ca1fa9e48992f7ec68e47f
  • Fixes #1 (closed).
• Change to a PEP 517 based workflow
• Change to SPDX license identifier
  • https://github.com/hgrecco/pint/blob/0.19.2/LICENSE
• upgpkg: python-pint 0.22
  • Related python-xarray#1 (closed).
• upgpkg: python-pint 0.23
  • New test failures https://github.com/hgrecco/pint/issues/1898