[CLEANUP] Streamline code in UpgradeWizard

* Correct naming of Updates (old name UpgradeWizards) and variables
* Use makeInstance instead of getUserObj
* Correct typehints

Resolves: #62408
Releases: master
Change-Id: Iecae292eada373b20f963d3daa0412758d654e27
Reviewed-on: http://review.typo3.org/33478
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>