[TASK] Move classAliasMaps into compatibility6 extension part 5

This is the sysext:extbase class alias part

Change-Id: I32923fe8b7f07c45abc1e42791ff9cd83c362897
Resolves: #62896
Related: #62013
Releases: master
Reviewed-on: http://review.typo3.org/34031
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>