Add support for single-method Laravel Accessors and Mutators

[pxpm]

WHY

BEFORE - What was wrong? What was happening before this PR?

As reported in #4163 , a new feature introduced by Laravel laravel/framework#40022 allow developers to setup acessors and mutators using a different syntax. Backpack guessing abilities were broken by this change, as this functions would look similar to relation functions.

AFTER - What is happening after this PR?

You can safely use the new Laravel feature.

HOW

How did you achieve that, in technical terms?

I prepared the grounds for us to move towards requiring return types in the relation functions that developer wants Backpack to guess from. I moved all logic that deals with checking method properties to a single method to reduce the margin of error until we don't make the change I talked before.

Added a check for the function return type, since the new Laravel feature requires the developer to define the return type, we can safely exclude them from beeing relationships.

Also added a check for method visibility as relationships methods are always public.

Still not perfect until we enforce the return types, but is better than yesterday! 👍

Is it a breaking change or non-breaking change?

non-breaking

How can we test the before & after?

Try adding the new Laravel feature in Monster model for example, before it would error. After it would work 👍

// text is a monster field that we want to mutate, not a relationship
protected function text(): Attribute {
        return new Attribute(
            get: fn($value) => ucfirst($value),
        );
    }

[tabacitu]

Purrfect... Thank you @pxpm . I've just changed the method name, that's all.

Merging!