Merge branch '6.4' into 7.0

* 6.4: (26 commits)
  [AssetMapper] Fix: also download files referenced by url() in CSS
  [AssetMapper] Fix eager imports are not deduplicated
  [Mime] Add `TemplatedEmail::$locale` to the serialized props
  fix tests
  add return types to test fixtures
  fix merge
  [Cache] Get TRUNCATE statement from platform
  do not detect the deserialization_path context value twice
  fix detecting the database server version
  [Cache] Add url decoding of password in `RedisTrait` DSN
  [Serializer] Remove incompatible type declaration with PHP 7.2
  [Serializer] Fix test
  Fix denormalizing empty string into object|null parameter
  [PropertyInfo] Fixed promoted property type detection for `PhpStanExtractor`
  [Serializer] Move discrimination to abstract
  [Serializer] Fix deserialization_path missing using contructor
  [Serializer] Fix access to private when Ignore
  [AssetMapper] Adding an option (true by default) to not publish dot files
  [AssetMapper] Fixing out-of-date test on Windows
  [HttpKernel] Fix logging deprecations to the "php" channel when channel "deprecation" is not defined
  ...

Author: fabpot

Mime/TemplatedEmail.php

@@ -100,7 +100,7 @@ public function markAsRendered(): void
      */
     public function __serialize(): array
     {
-        return [$this->htmlTemplate, $this->textTemplate, $this->context, parent::__serialize()];
+        return [$this->htmlTemplate, $this->textTemplate, $this->context, parent::__serialize(),  $this->locale];
     }
 
     /**
@@ -109,6 +109,7 @@ public function __serialize(): array
     public function __unserialize(array $data): void
     {
         [$this->htmlTemplate, $this->textTemplate, $this->context, $parentData] = $data;
+        $this->locale = $data[4] ?? null;
 
         parent::__unserialize($parentData);
     }

Tests/Mime/TemplatedEmailTest.php

@@ -43,12 +43,14 @@ public function testSerialize()
             ->textTemplate('text.txt.twig')
             ->htmlTemplate('text.html.twig')
             ->context($context = ['a' => 'b'])
+            ->locale($locale = 'fr_FR')
         ;
 
         $email = unserialize(serialize($email));
         $this->assertEquals('text.txt.twig', $email->getTextTemplate());
         $this->assertEquals('text.html.twig', $email->getHtmlTemplate());
         $this->assertEquals($context, $email->getContext());
+        $this->assertEquals($locale, $email->getLocale());
     }
 
     public function testSymfonySerialize()