Add support for class-based replacements instead of closures

[alissn]

Hi,

In this pull request (related to #2040), I added support for using class-based replacements instead of Closures.

Previously, when using Closures in replacement configuration, running the php artisan config:cache command caused the following error:

Your configuration files are not serializable.

To solve this, I introduced a new ReplacementKeyCommand class.
Replacements can now be implemented as dedicated classes, ensuring compatibility with config caching.

---

Example

Replacement classes:

<?php

namespace Modules\Test\Console\Replacements;

use Nwidart\Modules\Support\ReplacementKeyCommand;

class AuthorName extends ReplacementKeyCommand
{
    public function handle(): string
    {
        return 'Ali SSN';
    }
}

<?php

namespace Modules\Test\Console\Replacements;

use Nwidart\Modules\Support\ReplacementKeyCommand;

class ModuleStudlyName extends ReplacementKeyCommand
{
    public function handle(): string
    {
        return $this->generator->getName();
    }
}

Config file usage:

'composer' => [
    'LOWER_NAME',
    'STUDLY_NAME'   => \Modules\Test\Console\Replacements\ModuleStudlyName::class,
    'VENDOR',
    'AUTHOR_NAME'   => \Modules\Test\Console\Replacements\AuthorName::class,
    'AUTHOR_EMAIL',
    'MODULE_NAMESPACE',
    'PROVIDER_NAMESPACE',
    'APP_FOLDER_NAME',
],

---

This resolves the serialization issue and makes replacements more extendable and testable.
Fixes #2117.