Improve tests structure
    
    - rename test-reboot.yml to tests-reboot.yml so that it's run by CI directly
    - drop unnecessary tests.yml
    - add mandatory test.log, see
      https://docs.fedoraproject.org/en-US/ci/standard-test-interface/#_invocation
    - improve results.yml format
    - drop avc.err.log and log everything AVC related to avc.log