[TASK] Remove dummy files from ext:cms

This catches most old empty class files from ext:cms. The rest
needs to be taken care of in single patches.
The patch also changes all old mentions of the old class names,
mostly comments are affected.

Change-Id: I2b8ebfad178001c7bc8def967c01a56ae113c029
Resolves: #47792
Related: #47756
Releases: 6.2
Reviewed-on: https://review.typo3.org/20381
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn