[8.x] Fixed the appends property to work with the new Accessor method

[nickakitch]

When using the new attribute casting method from PR #40022 you are currently unable to include the method in the 'appends' property as you would when using the older method.

Currently:

$appends = ['title'];

public function title(): Attribute
{
    return ucfirst($this->name);
}

$model->toArray(); // throws a BadMethodCallException

This PR allows methods that return the Attribute object to be included in the 'appends' property

[taylorotwell]

Works fine for me - your attribute is not defined correctly?

public function title(): Attribute
{
    return new Attribute(
        fn ($value, $attributes) => ucfirst($attributes['name']),
    );
}

[nickakitch]

From the looks of things the case matters:

$appends = ['firstName']; // won't work
$appends = ['first_name']; // works

With the old method camel case also worked