Report hung system tests

Report hung system tests

At times, a problem might occur where a test is not responding,
especially in the CI, determining the specific test responsible can be
difficult. Fortunately, when running tests with the pytest runner,
pytest sets the PYTEST_CURRENT_TEST environment variable to the current
test nodeid and stage. Afterward, the variable can be examined to
identify the test that has stopped responding.

The monitoring script needs to be started in the background. Still, the
shell executor used for BSD and FIPS testing can't handle the background
process cleanly, and the script step will wait for the background
process for the entire duration of the background process (currently
3000 seconds). Therefore, run the monitoring script only when the Docker
executor is used where this is not a problem.