[FEATURE] Use the ckeditor plugin editorplaceholder

Enable the ckeditor plugin editorplaceholder which is available since
the update of ckeditor to version 4.15.0 with #92412 and fill it with
the placeholder information provided by the TCA.

Resolves: #92423
Releases: master
Change-Id: Ie392073d200a193b2be5f245042f0914f7665cdd
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65899


Tested-by: Torben Hansen <derhansen@gmail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Torben Hansen <derhansen@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>