Make the Collection::times callback optional

[CupOfTea696]

Follow up on #19276

Allows calls to Collection::times without the callback parameter, so you can create simple range collections and maybe modify them manually later with map or mapWithKeys methods.

Use case example:

Collection::times(2)->mapWithKeys(function ($number) {
    return ['slug-'.$number => 'Title '.$number];
})->toArray();


/**
 *   [
 *       ['slug-1' => 'Title 1'],
 *       ['slug-2' => 'Title 2']
 *   ]
 */