gh-97669: Fix test_tools reference leak (#98216)

gh-97669: Fix test_tools reference leak (#98216)

test_tools.test_sundry() now uses an unittest mock to prevent the
logging module to register a real "atfork" function which kept the
logging module dictionary alive. So the logging module can be
properly unloaded. Previously, the logging module was loaded before
test_sundry(), but it's no longer the case since recent test_tools
sub-tests removals.