Merge branch '7.4' into 8.1

* commit 'a2e989e26da':
  [Serializer] Fix denormalizing the discriminator type property when a name converter renames it
  [HttpFoundation] Make session handlers non-serializable
  [Validator] Update Swedish translation #64518
  [FrameworkBundle] Tolerate a newer DependencyInjection `ExtensionType` shape in the reference fixture

# Conflicts:
#	src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MigratingSessionHandler.php