Resolve #3455746 "A lazybuilder callbacks test update barcelona2024"

Closes #3455746 We updated the exception message to be more specific in the unit test.

core/lib/Drupal/Core/Render/Renderer.php

@@ -369,9 +369,11 @@ protected function doRender(array &$elements, RenderContext $context): string|Ma
       assert(is_array($elements['#lazy_builder']), 'The #lazy_builder property must have an array as a value.');
       assert(count($elements['#lazy_builder']) === 2, 'The #lazy_builder property must have an array as a value, containing two values: the callback, and the arguments for the callback.');
       assert(is_array($elements['#lazy_builder'][1]), 'The #lazy_builder argument for callback must have an array as a value.');
-      assert(count($elements['#lazy_builder'][1]) === count(array_filter($elements['#lazy_builder'][1], function ($v) {
-        return is_null($v) || is_scalar($v);
-      })), "A #lazy_builder callback's context may only contain scalar values or NULL.");
+      // Utilize an outer assertion to ensure array_walk() is only called when assertions are enabled.
+      assert(array_walk($elements['#lazy_builder'][1], function ($arg, $key) {
+        assert(is_null($arg) || is_scalar($arg),
+          "A #lazy_builder callback's context may only contain scalar values or NULL. Problem with parameter at array key: " . $key);
+      }));
       assert(!Element::children($elements), sprintf('When a #lazy_builder callback is specified, no children can exist; all children must be generated by the #lazy_builder callback. You specified the following children: %s.', implode(', ', Element::children($elements))));
       $supported_keys = [
         '#lazy_builder',