[5.0] Adding array_whitelist() and array_blacklist() functions

check if a value is whitelisted or blacklisted
useful for double checking url parameters like filters & sorts

Example: 
```php

/* Controller index */
public function index($sortBy = 'name')
{
    $sortBy = array_whitelist($sortBy, ['name', 'age', 'rank'], 'name');

    // ...
}

```
Btw, was following the example in the same file for the array_set() method. https://github.com/laravel/framework/blob/52c6960c39db7d25ece3597b7ceefd2093b33d8f/src/Illuminate/Support/Arr.php#L334-L337