[5.2] Fix a case with parameters of explicit depending rules

[themsaid]

As noted in #13047

This PR handles explicit depending rules when the explicit keys are non-numeric:

Validator::make(
    [
        'fields' => [
            'fr' => ['name' => '', 'content' => 'ragnar'],
            'es' => ['name' => '', 'content' => 'lagertha'],
        ]
    ],
    ['fields.*.name' => 'required_with:fields.*.content']
);

Before, it was only working with numeric keys [0, 1] rather than string keys ['fr', 'es'].