[11.x] Container shares fixed values/initialized instances instead of singleton closure resolutions

[seriquynh]

Inside tests, there are a few fixed values/initialized instances that can be shared instead of being resolved via callbacks. Eg:

$this->container->singleton(Registrar::class, function () {
    return $this->router;
});

// container->make() will return same instance like the code above.
$this->container->instance(Registrar::class, $this->router);

[seriquynh]

$nextParam and $next are useless because they do nothing and don't have any assertions. This test is to ensure if right parameters are passed to Authorize::handle() methods.