Breaking: #83241 - Extbase: Removed custom functionality for DataMapper->getPlainValue

See forge#83241

Description

Extbase's DataMapper allowed for wrapping string values in custom user functions via custom parameters. This was primarily placed in DataMapper for allowing TYPO3's legacy DBAL / $GLOBALS['TYPO3_DB'].

The functionality is now removed, as the Generic Backend is handled via Doctrine DBAL.

Impact

Calling DataMapper->getPlainValue() with the third or fourth parameter set will have no effect anymore.

Affected Installations

In an VERY unlikely case of using a custom Persistence Backend within Extbase in an extension, some transformations will not work as expected anymore.

Migration

Use the transformations outside the DataMapper, if still necessary.