[TASK] Move classAliasMaps into compatibility6 extension part 2

This is the sysext:core class alias part

Resolves: #62611
Related: #62013
Releases: master
Change-Id: Iaa38059249423fda9d77f00d9fb42268c08d9e88
Reviewed-on: http://review.typo3.org/33171
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>