[BUG] Running functional tests with virtual fields leads to error

[calien666]

The Core Testing Framework needs fields defined in TCA set up in database.

As this behaviour crashes code inside this extension and detection of set fields doesn't work correctly, it is needed to define own NodeTypes for the Backend allowing DataHandler passing through the data without trying to persist.
Additionally, database field creation has to be prevented. This should also be future safe, as TYPO3 v13 will use TCA for schema creation.