[Console] Fix symfony#5897 - Console component require Shell component

When setting the process isolation of a shell to true: `setProcessIsolation(true)` throw a `\RuntimeException` if the Process component isn't available.

Author: alias-mac

src/Symfony/Component/Console/Shell.php

@@ -203,5 +203,9 @@ public function getProcessIsolation()
  public function setProcessIsolation($processIsolation)
  {
  $this->processIsolation = (Boolean) $processIsolation;
+
+ if ($this->processIsolation && !class_exists('Symfony\\Component\\Process\\Process')) {
+ throw new \RuntimeException('Unable to isolate processes as the Symfony Process Component is not installed.');
+ }
  }
 }