Merge branch '3.4' into 4.4

* 3.4:
  [Http Foundation] Fix clear cookie samesite
  [Security] Check if firewall is stateless before checking for session/previous session
  [Form] Support customized intl php.ini settings
  [Security] Remember me: allow to set the samesite cookie flag
  [Debug] fix for PHP 7.3.16+/7.4.4+
  [Validator] Backport translations
  Prevent warning in proc_open()

Author: nicolas-grekas

Process.php

@@ -336,7 +336,7 @@ public function start(callable $callback = null, array $env = [])
             throw new RuntimeException(sprintf('The provided cwd "%s" does not exist.', $this->cwd));
         }
 
-        $this->process = proc_open($commandline, $descriptors, $this->processPipes->pipes, $this->cwd, $envPairs, $options);
+        $this->process = @proc_open($commandline, $descriptors, $this->processPipes->pipes, $this->cwd, $envPairs, $options);
 
         if (!\is_resource($this->process)) {
             throw new RuntimeException('Unable to launch a new process.');