[TASK] Use labels and modal in Site module

Use labels instead of hardcoded text and a modal
asking users if a site configuration should be really deleted.

Resolves: #86078
Releases: master
Change-Id: I49de820ef5e48f88c6449872cfee2eca617c46eb
Reviewed-on: https://review.typo3.org/58121


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>