[TASK] Fix PHP 8 compatibility issues part 4/x

Milestone: With a last series of type handling and
array access fixes throughout core and in
typo3/testing-framework, a first set of functional
pre-merge tests can be enabled with PHP 8.0.

composer req --dev typo3/testing-framework:^6.7.2

Resolves: #93686
Releases: master
Change-Id: I2d35725967be563fe9408083ee8aee59ea1533e3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68294


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Benni Mack <benni@typo3.org>