TASK
Update requirements for TYPO3 13
Migrate plugin registration
Remove obsolete ext_tables.php
Migrate registration of status dashboard widget, docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/12.0/Breaking-96812-NoFrontendTypoScriptBasedTemplateOverridesInTheBackend.html
Don't use QueryBuilder->add() anymore because it has been removed, docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/13.0/Breaking-102875-QueryBuilderChanges.html
Remove language-related function from AbstractPlugin and use custom translate function instead
Migrate database queries to use type constants from Connection instead of PDO, docs.typo3.org/m/typo3/reference-coreapi/main/en-us/ApiOverview/Database/QueryBuilder/Index.html
Remove obsolete code for TYPO3 11 and below
Migrate FlexForm definition
Migrate database queries
Set fallback values for indexer starting pages
Use FileResourceFactory instead of fileRepository->findFileReferenceByUid()
Don't use deprecated method getTwoLetterIsoCode() anymore, replace with getTypo3Language() and getWebsiteTitle()
Remove $frontendController from AbstractPlugin
Make $request and $languageId public in PluginBase
Migrate usage of MathUtility::convertToPositiveInteger()
Migrate usage of $pageRepository->enableFields()
Migrate usage of $GLOBALS['TSFE']->sys_page->getRecordOverlay()
Migrate usage of $cObj->crop()
Remove usage of $GLOBALS['TSFE']->register
Fix return type of PageRepository->checkRecord() for TYPO3 12