[TASK] Clean-up in site handling

- add void return types
- add access modifiers for constants
- fix some null coalescing
- remove superfluous comments
- add newline before namespace

Resolves: #84662
Releases: master
Change-Id: I1288b27b1edbd99b0624a66a5fb01cd02547b5ec
Reviewed-on: https://review.typo3.org/56602


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>