[11.x] apply excludeUnvalidatedArrayKeys to list validation

[lorenzolosa]

Laravel 11 introduced a list validation rule (with #50454). However, the Validator::excludeUnvalidatedArrayKeys() feature was not extended to work with list; this PR fixes that.

Intuitively, I would expect list to work exactly as array + ensuring that the array is a list. However, in the case of a list of arrays, extra fields in subarrays are always included when validating the top-level field with the list rule and without the array rule. Even adding the array rule to the subarrays doesn't solve the issue.

With this PR, extra fields are excluded from arrays, regardless of whether the top-level field is array or list. A test is included.

Issues with the current behaviour

Assume that we have the following data to validate:

$data = [
    'field' => [
        [
            'sub' => 'aaa',
            'extra' => 'bbb',
        ],
    ],
];

If we validate it with:

$rules = [
    'field' => 'array',
    'field.*.sub' => 'string',
];

then the extra field is not included in Validator::make($data, $rules)->validated(); but is included with the following rules:

$rules = [
    'field' => 'list',
    'field.*.sub' => 'string',
];

and not even with:

$rules = [
    'field' => 'list',
    'field.*' => 'array',
    'field.*.sub' => 'string',
];

I would argue that the list rule should be coherent with the array rule; but even if we allow it not to be, I believe that failing to exclude unvalidated array keys when the array rule is explicitly included in the last example is an issue.