Update PHP and PHPUnit across all packages; fix ext-rdkafka requirement

Author: andrewmy

composer.json

@@ -13,7 +13,7 @@
         "symfony/process": "^4.3|^5"
     },
     "require-dev": {
-        "phpunit/phpunit": "~7.5",
+        "phpunit/phpunit": "^9.5",
         "symfony/dependency-injection": "^4.3|^5",
         "symfony/config": "^4.3|^5",
         "symfony/http-kernel": "^4.3|^5",