IBX-8118: Implemented RemoveLegacyClassAliasRector rule

[alongosz]

🎫 Issue	IBX-8118

Description:

This PR defines the first rule, to remove our BC layer class_alias statements from the codebase.

Usage

Create ./rector.php:

<?php

/**
 * @copyright Copyright (C) Ibexa AS. All rights reserved.
 * @license For full copyright and license information view LICENSE file distributed with this source code.
 */
declare(strict_types=1);

use Ibexa\Rector\Rule\Internal\RemoveLegacyClassAliasRector;
use Rector\Config\RectorConfig;

return static function (RectorConfig $rectorConfig): void {
    $rectorConfig->paths(
        [
            __DIR__ . '/src', // see if it matches your project structure
            __DIR__ . '/tests',
        ]
    );

    $rectorConfig->rule(RemoveLegacyClassAliasRector::class);
};

For QA:

Optionally, check if the rector rule works as expected.

Documentation:

No doc needed, this is an internal rule.