Merge branch '7.4' into 8.0

* 7.4: (21 commits)
  [ObjectMapper] lazy loading
  [Filesystem] Unify logic for isAbsolute() in Path
  [DependencyInjection] Include return type in AppReference shape
  [Finder] Make method calls explicit in ExcludeDirectoryFilterIterator
  [Cache] Remove unset call on undefined variable in PhpArrayAdapter
  [Twig] Ensure WrappedTemplatedEmail::getReturnPath() returns a string
  [Routing] Simplify importing routes defined on controller services
  Fix tests
  [DependendcyInjection] Improve shape for "from_callable" definitions
  [PHPDoc] Fix various PHPDoc syntax errors
  [Console] Add missing VERBOSITY_SILENT case in CommandDataCollector
  [Notifier] Remove unused $transportName argument in EmailChannel::notify()
  [Translation] Remove an unused argument passed to parseNode() method
  [HttpClient] Reject 3xx pushed responses
  [Serializer] Use Asia/Tokyo instead of Japan in tests
  [ProxyManagerBridge] Remove comment that reference github discussion
  [JsonPath] Remove unused "nothing" property from JsonCrawler
  [ErrorHandler] Improve PHPDoc precision in SerializerErrorRenderer
  [Routing] Fix matching the "0" URL
  [Form] Fix EnumType choice_label logic for grouped choices
  ...

Adapter/PhpArrayAdapter.php

@@ -324,7 +324,7 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
         file_put_contents($tmpFile, $dump);
         @chmod($tmpFile, 0o666 & ~umask());
-        unset($serialized, $value, $dump);
+        unset($value, $dump);
 
         @rename($tmpFile, $this->file);
         unset(self::$valuesCache[$this->file]);