Epic #83968: PSR-11 Initiative
Consolidate singleton usage
There is Bootstrap::getInstance()->getEarlyInstance() and
GeneralUtility::makeInstance() to retrieve (global) instances.
Sometimes the former, sometimes the latter is used (e.g. to
retrieve the PackageManager).
As there is no obvious reason why diffrent methods are used, this
should be unified to one way to retrieve singletons.
Furthermore classes should not know whether something is an
early instance or not. Implementation details like that
should be abstracted into a singleton container.
That (currently) is GeneralUtility::makeInstance().