[!!!][TASK] Move interfaces of dashboard

The interfaces of the dashboard have been moved out of the
interfaces folder to be consistent with the overall TYPO3 structure.

Additionally, the superfluous button utility has been removed.

Releases: master
Resolves: #91066
Change-Id: Iaad0c1d8d046b467ee44d8cbbe32f8803c737fae
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64201


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Richard Haeser <richard@maxserv.com>