Migrate dirinstall gating test from STI to TMT
    
    The Fedora rawhide CI tests are used.
    
    This pull request enables tests in the RHEL gating using `tmt` which
    also allows to easily execute and debug tests from your laptop:
    
    Run tests directly on your localhost:
    
        sudo dnf install -y tmt
        tmt run --all provision --how local
    
    Run tests in a virtual machine:
    
        sudo dnf install -y tmt-provision-virtual
        tmt run
    
    Check the documentation to learn more about the tool:
    https://docs.fedoraproject.org/en-US/ci/tmt/
    
    Related: rhbz#2006718