Create a tmt-owned COPR project for artifact provider tests

[vaibhavdaren]

Problem

The current COPR repository artifact provider tests use the `mariobl/pyspread` COPR project, which only provides chroots for Fedora 43+. This means the tests are gated and cannot run on older Fedora releases, rawhide, or CentOS, making coverage fragile and dependent on a third-party project outside of tmt's control.

This was raised by @LecrisUT during review of PR #4723, #4695.

Proposed Fix

Create a tmt-owned COPR project specifically for CI/testing purposes that:

• Is owned/maintained by the `teemtee` organization
• Has auto-branching enabled so it automatically tracks new Fedora and CentOS Stream releases
• Works on both Fedora and CentOS Stream
• Is not tied to any specific distro version
• Contains a simple, stable package (e.g., a minimal dummy RPM) reliably built and available

This would make the COPR artifact provider tests self-sufficient and not dependent on any external COPR project.

References

• Discussed in PR Simpler branching for verify-installation tests #4723: Simpler branching for verify-installation tests #4723
• Discussed in PR copr.repository provider creates a Repository object #4695: copr.repository provider creates a Repository object #4695