Pass {USER, COREOS}_DATA separately in testcloud

[frantisekz]

Together with now staged testcloud-0.11.0, should resolve https://github.com/teemtee/tmt/issues/3235 once and for all.

Required testcloud is built at: https://copr.fedorainfracloud.org/coprs/frantisekz/testcloud-temp/

The {USER, COREOS}_DATA variables were affected by threads overwriting them directly in testcloud's config object as observed in https://github.com/teemtee/tmt/pull/3244#issuecomment-2392236256 and following comments. Testcloud-side change can be seen here: https://pagure.io/testcloud/c/ee1202bcf57cd475f4586f3693e2127f9a12e92e?branch=master .

Only these two variables can differ between various instances in tmt's use of testcloud, the others are kept separately since the domain api switchover last year: https://github.com/teemtee/tmt/pull/2078 .

Co-authored by @jskladan

@happz @psss

Pull Request Checklist

• [x] implement the feature
• [ ] write the documentation
• [ ] extend the test coverage
• [ ] update the specification
• [ ] adjust plugin docstring
• [ ] modify the json schema
• [ ] mention the version
• [ ] include a release note