Breaking: #73504 - Make TimeTracker a singleton

See forge#73504

Description

The class \TYPO3\CMS\Core\TimeTracker\TimeTracker has been marked as singleton and is no longer stored in $GLOBALS['TT'].

Impact

Using methods of $GLOBALS['TT'] will result in a fatal error.

Affected Installations

All installations or 3rd party extensions using $GLOBALS['TT'].

Migration

Use \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\TimeTracker\TimeTracker::class) instead.