[ticket/12620] Use the test environment for the tests

PHPBB3-12620

tests/di/fixtures/config/test/config.yml

@@ -0,0 +1,2 @@
+core:
+    require_dev_dependencies: true

tests/di/fixtures/config/test/container/environment.yml

@@ -0,0 +1,14 @@
+parameters:
+    core: true
+
+services:
+    config.php:
+        synthetic: true
+
+    dbal.conn:
+        class: phpbb\db\driver\factory
+        arguments:
+            - @service_container
+
+    dispatcher:
+        class: phpbb\db\driver\container_mock