[TASK] Streamline array access and constructor definition of SiteWriter

Resolves: #105128
Releases: main
Change-Id: Iaf60058a317ab34b228a0bfd29b648defc17844e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/86346


Reviewed-by: Thomas Hohn <tho@gyldendal.dk>
Tested-by: Garvin Hicking <gh@faktor-e.de>
Reviewed-by: Guido Schmechel <guido.schmechel@brandung.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Thomas Hohn <tho@gyldendal.dk>
Reviewed-by: Chris Müller <typo3@brotkrueml.dev>
Reviewed-by: Garvin Hicking <gh@faktor-e.de>