[ticket/12597] Command for executing all available cron tasks

Command cron:execute-all executes all available cron tasks.
Test files in tests/console/cron folder

PHPBB3-12597

tests/console/cron/tasks/simple_ready.php

@@ -0,0 +1,13 @@
+<?php
+
+class phpbb_cron_task_core_simple_ready extends \phpbb\cron\task\base
+{
+	public function get_name()
+	{
+		return get_class($this);
+	}
+
+	public function run()
+	{
+	}
+}