[BUGFIX] Prevent infinite site settings cache recreation

Site settings rely on the Settings base class __set_state() method
to recreate the object from cache.
Since the base class used `new self` instead of `new static`,
the object received an invalid type and was therefore ignored.

Use `new static` to ensure the correct constructor is invoked.

Resolves: #104945
Related: #104858
Releases: main
Change-Id: I09eee1043902b5e62243258a080a64f026a6783e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/86074


Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Garvin Hicking <gh@faktor-e.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: Garvin Hicking <gh@faktor-e.de>