[TASK] Raise PHPStan to version 1.5.6

The new version finds some new possible bugs and
removes some incorrect ones.

Also update phpstan/phpstan-phpunit.

Used commands:
> composer req --dev phpstan/phpstan:^1.5.6
> composer req --dev phpstan/phpstan-phpunit:^1.1.0
> Build/Scripts/runTests.sh -s phpstanGenerateBaseline

Resolves: #97397
Releases: main, 11.5
Change-Id: I052ba01b33582f3f18f49c0ee2375f63d1048f4b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74325


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Benni Mack <benni@typo3.org>