Merge branch '5.0' into 5.1

* 5.0:
  Fix abstract method name in PHP doc block
  Various cleanups
  [HttpClient] fix issues in tests
  Fixes sprintf(): Too few arguments in form transformer
  [Console] Fix QuestionHelper::disableStty()
  [Validator] Use Mime component to determine mime type for file validator
  validate subforms in all validation groups
  Update Hungarian translations
  Add meaningful message when Process is not installed (ProcessHelper)
  [PropertyAccess] Fix TypeError parsing again.
  [TwigBridge] fix fallback html-to-txt body converter
  [Security/Http] fix merge
  [ErrorHandler] fix setting $trace to null in FatalError
  [Form] add missing Czech validators translation
  [Validator] add missing Czech translations
  never directly validate Existence (Required/Optional) constraints

Author: nicolas-grekas

Server/DumpServer.php

@@ -41,7 +41,7 @@ public function __construct(string $host, LoggerInterface $logger = null)
     public function start(): void
     {
         if (!$this->socket = stream_socket_server($this->host, $errno, $errstr)) {
-            throw new \RuntimeException(sprintf('Server start failed on "%s": '.$errstr.' '.$errno, $this->host));
+            throw new \RuntimeException(sprintf('Server start failed on "%s": ', $this->host).$errstr.' '.$errno);
         }
     }