Merge branch '3.4' into 4.1

* 3.4:
  [Debug] ignore underscore vs backslash namespaces in DebugClassLoader
  [TwigBridge][Form] Prevent multiple rendering of form collection prototypes
  [FrameworkBundle] fix describing routes with no controllers
  [DI] move RegisterServiceSubscribersPass before DecoratorServicePass
  Update ValidationListener.php
  [Yaml] ensures that the mb_internal_encoding is reset to its initial value
  [WebLink] Fixed documentation link
  [Security] getTargetPath of TargetPathTrait must return string or null
  [Hackday][Serializer] Deserialization ignores argument type hint from phpdoc for array in constructor argument
  [Security] defer log message in guard authenticator
  merge conflicts
  Fix HeaderBag::get phpdoc

Author: nicolas-grekas

Resources/views/Form/form_div_layout.html.twig

@@ -28,7 +28,7 @@
 {%- endblock form_widget_compound -%}
 
 {%- block collection_widget -%}
-    {% if prototype is defined %}
+    {% if prototype is defined and not prototype.rendered %}
         {%- set attr = attr|merge({'data-prototype': form_row(prototype) }) -%}
     {% endif %}
     {{- block('form_widget') -}}