Breaking: #45899 - Split class ImportExport into classes Import and Export

See forge#45899

Description

Class TYPO3CMSImpexpImportExport (typo3/sysext/impexp/Classes/ImportExport.php) is split into a class dedicated for import and another one for export.

Impact

Using and extending the class is not possible any more.

Affected Installations

Those which use the class and its methods directly or extend the class.

Migration

Use or extend one or both of the new classes (TYPO3CMSImpexpImport and TYPO3CMSImpexpExport).