[Feature Request] Add Event Loop Lag to Server::stats()

[Avariya]

1. What did you do? If possible, provide a simple script for reproducing the error.

written with GPT blessing. But sure it can be done in native way

        Timer::tick(1000, static function () use ($eventLoopLagProvider) {
            static $lastTime = 0;
            $currentTime = microtime(true);
            if ($lastTime > 0) {
                /** @var float $eventLoopLag */
                $eventLoopLag = ($currentTime - $lastTime - 1) * 1000;
                $eventLoopLagProvider->setEventLoopLag($eventLoopLag);
            }

            $lastTime = $currentTime;
        });

2. What did you expect to see?

prometheus gauge static with actual event loop lag value in ms 

3. What did you see instead?

 nothing

4. What version of OpenSwoole are you using (show your php --ri openswoole)?

any