[php-src] Issue #21478: Property access on lazy proxy may invoke magic method despite real instance guards

Issue: https://github.com/php/php-src/issues/21478
Author: arnaud-lb

### Description

The following code:

```php
<?php

class Foo {
    public $_;

    public function __get($name) {
        global $proxy;
        printf("__get(\$%s) on %s\n", $name, $this::class);
        return $proxy->{$name};
    }
}

class Bar extends Foo {}

$rc = new ReflectionClass(Bar::class);
$proxy = $rc->newLazyProxy(function () {
    echo "Init\n";
    return new Foo();
});

$real = $rc->initializeLazyObject($proxy);
$real->x;

?>
```

Resulted in this output:
```
Init
__get($x) on Foo
__get($x) on Bar
```

But I expected this output instead:
```
Init
__get($x) on Foo
```

See https://github.com/php/php-src/pull/21463#pullrequestreview-3969097521.

### PHP Version

```plain
PHP 8.4
```

### Operating System

_No response_