[11.x] Add fluent helper

[PhiloNL]

The fluent helper seems to be a great addition to the collect helper when working with multi-dimension arrays and people seem to like it and suggested to PR it into the core:

$data = [
    'user' => [
        'name' => 'Philo',
        'address' => [
            'city' => 'Amsterdam',
            'country' => 'Netherlands',
        ]  
    ],
    'posts' => [
        [
            'title' => 'Post 1',                
        ],
        [
            'title' => 'Post 2',               
        ]
    ]
];

❌ collect($data)->get('user');
✅ fluent($data)->user

❌ collect($data)->get('user')['name'];
✅ fluent($data)->get('user.name');

❌ collect(collect($data)->get('posts'))->pluck('title');
✅ fluent($data)->collect('posts')->pluck('title');

❌ json_encode(collect($data)->get('user')['address']);
✅ fluent($data)->scope('user.address')->toJson();