Ensure DBAL custom type doesn't exists (#35704)

As the DBAL type registry is a static singleton, when running multiple tests, type may be already registered.

src/Illuminate/Database/DatabaseServiceProvider.php

@@ -123,7 +123,9 @@ protected function registerDoctrineTypes()
         $types = $this->app['config']->get('database.dbal.types', []);
 
         foreach ($types as $name => $class) {
-            Type::addType($name, $class);
+            if (! Type::hasType($name)) {
+                Type::addType($name, $class);
+            }
         }
     }
 }