Fix loss of parent slug

[alexrififi]

In case of using a third-party field inherited from Illuminate\Http\Resources\MergeValue the Tab is losing slug.

Example

We used naoray/nova-json

// in app/Nova/Resource.php

use Eminiarts\Tabs\Tabs;
use Eminiarts\Tabs\Tab;
use Naoray\NovaJson\JSON;

public function fields()
{
    return [
        Tabs::make('Tabs', [
            Tab::make('Settings', [
                JSON::make('Some Json Column Name', [
                    Text::make('First Field'),
                    Text::make('Second Field'),
                    Text::make('Third Field'),
                ]);
            ])->name('tab-slug'),
        ]),
    ];
}

In this case slug of tab Settings will be settings, not tab-slug.
Kind of weird.

This PR fixes this situation.

[RVxLab]

Sorry I merged this so late.

Thank you for providing a fix!