Allow building without poetry

[nphilipp]

Story

As a package maintainer, I want to build rpmautospec without poetry, so that I don’t have to install it and all its dependencies.

Acceptance Criteria

• [x] rpmautospec ships with setup.py #134
• [x] The RPM spec file allows conditionally building using setuptools instead of poetry

[nphilipp]

Building packages for F39, 40, Rawhide, EPEL9 from here: https://src.fedoraproject.org/rpms/python-rpmautospec/c/b69a39d380fc17ff3c8a068f8933fb3298cebbfe