Document #[RequiredBundle], ServicesBundle and ConsoleBundle

[lacatoire]

Fixes #22223

[GromNaN]

When using the ConsoleBundle alone, we should document the expected entrypoint:

use App\Kernel;
use Symfony\Component\Console\Application;

if (!is_dir(dirname(__DIR__).'/vendor')) {
    throw new LogicException('Dependencies are missing. Try running "composer install".');
}

if (!is_file(dirname(__DIR__).'/vendor/autoload_runtime.php')) {
    throw new LogicException('Symfony Runtime is missing. Try running "composer require symfony/runtime".');
}

require_once dirname(__DIR__).'/vendor/autoload_runtime.php';

return function (array $context) {
    $kernel = new Kernel($context['APP_ENV'], (bool) $context['APP_DEBUG']);
    $kernel->boot();

    return new Application('Application Name', 'Version', $kernel->getContainer());
};