PhpStan: Add strict mode check (pimcore#15115)

* PhpStan: Add strict mode check

* Update baseline

Author: blankse

composer.json

@@ -139,6 +139,7 @@
     "codeception/codeception": "^5.0.3",
     "codeception/module-symfony": "^3.1.0",
     "codeception/phpunit-wrapper": "^9",
+    "ergebnis/phpstan-rules": "^2.0",
     "phpstan/phpstan": "1.10.5",
     "phpstan/phpstan-symfony": "^1.2.20",
     "phpunit/phpunit": "^9.3",