After refactoring (#37430 and #36740) gives us more flexibility, we may be able to put them in the subfolder.

• cypari -> pypi/cypari2
• dateutil -> pypi/python-dateutil

The format is intended to match the PURL, see https://peps.python.org/pep-0725/#concrete-package-specification-through-purl, #37250

• Depends on sage --package, sage-get-system-packages: Support PURLs pkg:pypi/DISTRO-NAME, obtain dependencies of wheels from PyPI #37500
• Depends on Refactor bootstrap, bootstrap-conda, m4/sage_spkg_collect.m4, sage-spkg-info through sage --package properties, sage-get-system-packages #37430
• Depends on Refactor bootstrap-conda, m4/sage_spkg_collect.m4 through sage-package; handle dependencies_build #36740

Component: packages: standard

Issue created by migration from https://trac.sagemath.org/ticket/31136