Use QVERIFY2() with QTemporaryDir/File::errorString() consistently.
Attempt to catch issues like the below warning and follow-up issues.
QSYSTEM: tst_QFiledialog::clearLineEdit() QFileSystemWatcher: FindNextChangeNotification failed for "C:\Users\qt\_____aaaaaaaaaaaaaaaaaaaaaa" (Access is denied.)
Task-number: QTBUG-47370
Change-Id: I58a6e87c502627e976efa62ad73c912f3b2d49fa
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@theqtcompany.com>