[TASK] Isolate content element previews for page module

With the new strong defaults some content elements have moved to
the extensions mediace, css_styled_content and compatibility6.
The previews for the page module have not been moved.

This patch moves some previews to the corresponding extensions.

Resolves: #65952
Related: #65922
Releases: master
Change-Id: Idecf1b92b685237f7957e60a902afebd1010ba23
Reviewed-on: http://review.typo3.org/38154


Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>