[TASK] Backwards compatibility up to TYPO3 9

Classes/Controller/ConsentController.php

Classes/Controller/OptinController.php

Classes/Controller/StatisticsController.php

Classes/Controller/V9ConsentController.php

Classes/Controller/V9OptinController.php

Classes/Controller/V9StatisticsController.php

Classes/Service/JsonImportService.php

Classes/Service/OptinHistoryService.php

Classes/Traits/InitControllerComponents.php

Classes/ViewHelpers/V9/Backend/ControlViewHelper.php

Classes/ViewHelpers/V9/Backend/EditOnClickViewHelper.php

Classes/ViewHelpers/V9/Backend/IconViewHelper.php

.../ViewHelpers/V9/Backend/IsVersionHigherThanViewHelper.php

Classes/ViewHelpers/V9/Be/Menus/ActionMenuItemViewHelper.php

...ewHelpers/V9/Be/Menus/ActionMenuOptionGroupViewHelper.php

Contrib/mustache/src/Mustache/Tokenizer.php

Resources/Private/Layouts/V9Default.html

Resources/Private/Partials/V9/ButtonBar.html

Resources/Private/Partials/V9/DocHeader.html

Resources/Private/Partials/V9/License.html