Expose actual guest HW description in guest topology

[happz]

Related to https://github.com/teemtee/tmt/issues/2402. The patch bootstraps hardware field in the guest topology content, and populates it it very basic content. Extending it with more info, e.g. disk or system, will be task for future patches.

Pull Request Checklist

• [x] implement the feature
• [x] write the documentation
• [ ] extend the test coverage - filed https://github.com/teemtee/tmt/issues/2585 for more
• [x] update the specification
• [x] mention the version
• [ ] include a release note