[TASK] Tighten tests and extend PHP 8.1 testing

The big win with this patch: All core now run tests with E_ALL
error handling (unit, functional, acceptance). This means, they
will also fail when PHP deprecations are raised. This improves
PHP compatibility and makes sure new PHP versions can be integrated
more quickly since we'll find deprecated PHP code calls early.

Additionally, the acceptance tests are extended to run with PHP 8.1.
As a result, the entire testing is now done with PHP 8.1 and green,
we can claim PHP 8.1 compatibility for core now.

Resolves: #95981
Releases: master
Change-Id: I1eece6d2faec6453ada9731fc4064076dc8d5d97
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72151


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>