CI test updates
    
    - Add upstream testsuite tests/Regression/upstream-testsuite
      to the CI testplan.  However, this one isn't a good measure
      for gating, because it is too complex and flaky.  But it's
      good to have test results at hand.  This testcase reports a
      failure only in case of an infrastructure problem.  Individual
      .exp test failures are not a show stopper from the persp of
      the CI gating.
    - Add upstream systemtap build and install pseudo testcase.
      tests/Install/upstream-systemtap to the testplan.
      This one is disabled by default (in its main.fmf file).  The
      point here is to be able to test with upstream version of
      systemtap in case a working fedora build isn't available.
      This is a helper for manual testing, although if enabled, it
      will do its job in the automated CI pipeline too.
    - Use FMF tag instead of tier attributes to define the testplan.
    - Testcase updates:
      * tests/Regression/second-command-not-captured
      * tests/Regression/python-probing