Issue #3384960 by mondrake, daffie: Strengthen TransactionManager

core/lib/Drupal/Core/Database/Connection.php

core/lib/Drupal/Core/Database/Transaction.php

core/lib/Drupal/Core/Database/Transaction/StackItem.php

...upal/Core/Database/Transaction/TransactionManagerBase.php

...Core/Database/Transaction/TransactionManagerInterface.php

core/misc/cspell/dictionary.txt

...Tests/Core/Database/DriverSpecificTransactionTestBase.php