[5.8] getNamespace is independent

[seriquynh]

Application::getNamespace() currently uses global helpers in which the first call to this method is the call to global container instance only because Application constructor sets it via Application::registerBaseBindings(). Application::getNamespace() is independent and returns the namespace itself. This pull request solves by using the exact methods of Application rather than global helpers.

See the example below for more details:

• Step 1: The application laravel1/composer.json

{
    "autoload": {
        "psr-4": {
            "Laravel\\One\\": "app/"
        }
    }
}

• Step 2: The application laravel2/composer.json

{
    "autoload": {
        "psr-4": {
            "Laravel\\Two\\": "app/"
        }
    }
}

• Step 3: Create 2 application instances in a single process:

$app1 = new Application(realpath(__DIR__.'/path/to/laravel1'));
$app2 = new Application(realpath(__DIR__.'/path/to/laravel2'));
// Initialize but I haven't called getNamespace() from them.

Expected

$app1->getNamespace(); // "Laravel\\One\\"
$app2->getNamespace(); // "Laravel\\Two\\"

Actual

$app1->getNamespace(); // "Laravel\\Two\\"
$app2->getNamespace(); // "Laravel\\Two\\"

[driesvints]

@XuanQuynh please always provide the full description to your initial comment and not link to an external issue/pr.

[seriquynh]

@driesvints I updated (just copy from my earlier pr) . OK, I will provide on the later pull requests/issues.