Make `\Request::get` more performant.

Previously request get ran ALL searches regardless of whether a result was found. Now it only runs the ones required to find the value.
I would have written it this way:

```php
if ($this !== $result = $this->query->get($key, $this, $deep)) {
    return $result;
}

if ($this !== $result = $this->attributes->get($key, $this, $deep)) {
    return $result;
}

if ($this !== $result = $this->request->get($key, $this, $deep)) {
    return $result;
}

return $default;
```