bug symfony#58207 [TwigBridge] Avoid calling deprecated mergeGlobals() (derrabus)

This PR was merged into the 5.4 branch.

Discussion
----------

[TwigBridge] Avoid calling deprecated mergeGlobals()

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Follows twigphp/Twig#4283
| License       | MIT

`getGlobals()` is documented as the official replacement for `mergeGlobals()` despite being flagged ``@internal``. I've left a comment on the upstream PR.

Commits
-------

2883331 [TwigBridge] Avoid calling deprecated mergeGlobals()

Author: derrabus

src/Symfony/Bridge/Twig/Form/TwigRendererEngine.php

@@ -44,7 +44,7 @@ public function renderBlock(FormView $view, $resource, string $blockName, array
     {
         $cacheKey = $view->vars[self::CACHE_KEY_VAR];
 
-        $context = $this->environment->mergeGlobals($variables);
+        $context = $variables + $this->environment->getGlobals();
 
         ob_start();
 
@@ -164,7 +164,7 @@ protected function loadResourcesFromTheme(string $cacheKey, &$theme)
         // theme is a reference and we don't want to change it.
         $currentTheme = $theme;
 
-        $context = $this->environment->mergeGlobals([]);
+        $context = $this->environment->getGlobals();
 
         // The do loop takes care of template inheritance.
         // Add blocks from all templates in the inheritance tree, but avoid