Const TYPO3_MODE deprecated with TYPO3 v11

[lsoehn]

Const TYPO3_MODE gets deprecated with TYPO3 v11. Should be replaced with defined('TYPO3') or die(); as Security Gate in ext_localconf.php, ext_tables.php and Configuration/TCA/* . I think since changes are available with TYPO3 v10.4, we need some kind of versioning here @fpodschwadek .

See: https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/11.0/Deprecation-92947-DeprecateTYPO3_MODEAndTYPO3_REQUESTTYPEConstants.html#deprecation-92947