Add a coroutine monitoring the memory usage.

[kenashkov]

Add a new callback with Swoole\Timer::tick() on every second.
If the memory usage reaches 85% of memory limit clear 20% of all caches.
The cleanup is to be performed by invoking the controller action:
GuzabaPlatform\AppServer\Monitor\Controllers\Responder::clear_all_caches()

An additional argument for supporting what percentage is to be cleared like on clear_query_cache() is to be added as well.

The call of Timer::tick() is to done at worker startup. This can be done with adding a callback to the worker "_after_start" event. This is to be done with:

self::CONFIG_DEFAULTS[
    'services' => [
        'Events'
    ],
];

self::get_service('Events')->add_class_callback(WorkerStart::class, '_after_start', [$instance, 'method_name']);

See Guzaba2\Orm\Store\Memory.php::__construct()

LATER:
In the callback the user needs to be set to the SYSTEM user (the user is to be created first) with CurrentUser::set()

[kenashkov]

Add a Kernel::log($message) when this is triggered