Migrate cythonized archive build off of setuptools as a frontend

[andy-maier]

PR #2902 transitioned the pywbem distribution archive build away from using setup.py to using the "build" package.
That worked for the normal wheel archive, but not for the cythonized archive. PRs #2905 and #2906 were needed to get that back to work and right now, the cythonized archive is again built using setup.py.

This issue is to transition the build of the cythonized archive build off of setuptools as a frontend.