[TASK] Use phpunit configuration template for own testing

TF provides templates for unit- and functional testing,
with enhanced and hardened configuration options.

For own unit testing it has used the phpunit defaults,
which are not that strict as we want it to be.

Therefore, we use the template files now directly.

Releases: main, 7

.gitignore

@@ -3,3 +3,4 @@
 composer.lock
 public/
 Build/testing-docker/.env
+var/

Build/testing-docker/docker-compose.yml

@@ -117,11 +117,11 @@ services:
         php -v | grep '^PHP';
         if [ ${PHP_XDEBUG_ON} -eq 0 ]; then
           XDEBUG_MODE=\"off\" \
-          .Build/bin/phpunit Tests/Unit/;
+          .Build/bin/phpunit -c Resources/Core/Build/UnitTests.xml Tests/Unit/;
         else
           XDEBUG_MODE=\"debug,develop\" \
           XDEBUG_TRIGGER=\"foo\" \
           XDEBUG_CONFIG=\"client_host=host.docker.internal\" \
-          .Build/bin/phpunit Tests/Unit/;
+          .Build/bin/phpunit -c Resources/Core/Build/UnitTests.xml Tests/Unit/;
         fi
       "