[TASK] Update various dependencies to support PHP8

A few dependencies now have PHP8 support and PHP 7.2 support,
which we then update to the latest versions, also for v10.4.

Updated dev-dependencies:
* composer req "phpspec/prophecy:^1.12.2" --dev --with-all-dependencies
* composer req "friendsofphp/php-cs-fixer:^2.17.3" --dev --with-all-dependencies
* composer req "phpstan/phpstan:^0.12.64" --dev --with-all-dependencies
* composer req "phpunit/phpunit:^8.5.13" --dev --with-all-dependencies

Non-dev-dependency updates:
* composer req "nikic/php-parser:^4.10.4"

Also fix an undefined variable error that was introduced in #92497
and has now been discovered by the updated phpstan version.

Resolves: #93201
Releases: master, 10.4
Change-Id: Ic8839606ea05a0825a6e518dd644655ecc7c578e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67324


Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>