Add fixtures for deriving system test name from the directory name and
for a module-specific logger.
Add fixtures to execute shell and perl scripts. Similar to how run.sh
calls commands, this functionality is also needed in pytest. The
fixtures take care of switching to a proper directory, logging
everything and handling errors.
Note that the fixture system_test_dir is not defined yet. It is omitted
now for review readability and it's added in follow-up commits.
(cherry picked from commit 6886cc1826)
23cecd2190