Merge branch '5.1'

* 5.1:
  Internal classes are not legacy.
  [HttpFoundation] Skip the cookie_max_age fixture on PHP 8.
  add choice_translation_domain tests to prevent further regressions
  Update validators.tr.xlf

Author: fabpot

DeprecationErrorHandler/Deprecation.php

@@ -147,6 +147,10 @@ public function getMessage()
     public function isLegacy()
     {
         $class = $this->originatingClass();
+        if ((new \ReflectionClass($class))->isInternal()) {
+            return false;
+        }
+
         $method = $this->originatingMethod();
 
         return 0 === strpos($method, 'testLegacy')