[devtools] qunit: update to 1.18.0 (closes #5533333)
* the logging API has changed (register callbacks instead of setting
attributes on the QUnit object)
* the logging callbacks all have a single "details" object argument
* the "main" div was renamed to "qunit-fixture" (this change is
responsible for all the churn in our own JS test files)
* QUnit can now build the DOM elements it needs for reporting from a
single "qunit" div
change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')