runner/executor: Integrate igt_facts functionality

Modifies igt_runner to include calls to igt_facts() before the
execution of each test and after the final test concludes. Facts are
disabled by default, so add command line options to igt_runner to
enable facts:  -f, --facts

Updates serialize_settings() and read_settings_from_file() to save
and restore igt_runner settings to and from disk. This is used when
calling igt_runner with '--dry-run' and then by calling igt_resume
instead of igt_runner.

Updates unit testing for igt_runner to test that:
 - Facts are disabled by default
 - Facts can be enabled by command line arguments
 - The choice about facts being enabled or not is saved to disk
   and restored from disk

CC: Helen Koike <helen.koike@collabora.com>
CC: Jani Nikula <jani.nikula@linux.intel.com>
CC: Jani Saarinen <jani.saarinen@intel.com>
CC: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
CC: Juha-Pekka Heikkila <juha-pekka.heikkila@intel.com>
CC: Kamil Konieczny <kamil.konieczny@linux.intel.com>
CC: Lucas De Marchi <lucas.demarchi@intel.com>
CC: Maíra Canal <mcanal@igalia.com>
CC: Melissa Wen <mwen@igalia.com>
CC: Petri Latvala <adrinael@adrinael.net>
CC: Rob Clark <robdclark@chromium.org>
CC: Ryszard Knop <ryszard.knop@intel.com>
CC: Swati Sharma <swati2.sharma@intel.com>
CC: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
CC: dominik.karol.piatkowski@intel.com
CC: himal.prasad.ghimiray@intel.com
CC: katarzyna.piecielska@intel.com
CC: luciano.coelho@intel.com
CC: nirmoy.das@intel.com
CC: stuart.summers@intel.com
Reviewed-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Reviewed-by: Ryszard Knop <ryszard.knop@intel.com>
Reviewed-by: Dominik Karol Piątkowski <dominik.karol.piatkowski@intel.com>
Signed-off-by: Peter Senna Tschudin <peter.senna@linux.intel.com>