[BUGFIX] Ensure correct loading order in ModuleTemplate

This change makes sure to set up the page in the TYPO3 Backend,
to load JS and CSS directly in PageRenderer when the ModuleTemplate
object is instantiated, allowing to load custom JavaScript or CSS.

Before, renderContent (the last call in ModuleTemplate) was
used to add default CSS and JS.

Resolves: #91812
Releases: master, 10.4
Change-Id: I87c8392d3784d3ac63a086846e85fae76663d4a2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65236
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Marcus Schwemer <ms@schwemer.de>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Marcus Schwemer <ms@schwemer.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>

typo3/sysext/backend/Classes/Template/ModuleTemplate.php

@@ -246,6 +246,9 @@ public function __construct(
         $this->iconFactory = $iconFactory;
         $this->flashMessageService = $flashMessageService;
         $this->docHeaderComponent = GeneralUtility::makeInstance(DocHeaderComponent::class);
+        $this->setupPage();
+        $this->loadJavaScripts();
+        $this->loadStylesheets();
     }
 
     /**
@@ -363,11 +366,8 @@ public function getDocHeaderComponent()
      */
     public function renderContent()
     {
-        $this->setupPage();
-        $this->pageRenderer->setTitle($this->title);
-        $this->loadJavaScripts();
         $this->setJavaScriptCodeArray();
-        $this->loadStylesheets();
+        $this->pageRenderer->setTitle($this->title);
 
         $this->view->assign('docHeader', $this->docHeaderComponent->docHeaderContent());
         if ($this->moduleId) {

typo3/sysext/fluid/Classes/ViewHelpers/Be/ContainerViewHelper.php

@@ -83,7 +83,8 @@ public function render()
         $addJsInlineLabels = $this->arguments['addJsInlineLabels'];
         $includeRequireJsModules = $this->arguments['includeRequireJsModules'];
 
-        $pageRenderer = $this->getPageRenderer();
+        $moduleTemplate = $this->getModuleTemplate();
+        $pageRenderer = $moduleTemplate->getPageRenderer();
 
         // Include custom CSS and JS files
         if (is_array($includeCssFiles) && count($includeCssFiles) > 0) {
@@ -111,7 +112,6 @@ public function render()
         }
         // Render the content and return it
         $output = $this->renderChildren();
-        $moduleTemplate = $this->getModuleTemplate();
         if ($this->arguments['enableDocHeader'] ?? false) {
             $moduleTemplate->getDocHeaderComponent()->enable();
         } else {