Breaking: #73504 - Make TimeTracker a singleton 

See forge#73504

Description 

The class TYPO3CMSCoreTimeTrackerTimeTracker 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 TYPO3CMSCoreUtilityGeneralUtility::makeInstance(TYPO3CMSCoreTimeTrackerTimeTracker::class) instead.