[php-src] Issue #22271: Invalid case in ReflectionClass::getProperty

Issue: https://github.com/php/php-src/issues/22271
Author: jorgsowa

### Description

The following code:

```php
<?php
class C {
    public $p;
}

spl_autoload_register(function ($name) {
    echo "Autoloading $name\n";
});

$rc = new ReflectionClass('C');
try {
    $rc->getProperty("Some\\MixedCase::p");
} catch (ReflectionException $e) {
    echo $e->getMessage(), "\n";
}
```

Resulted in this output:
```
Autoloading some\mixedcase
Class "some\mixedcase" does not exist
```

But I expected this output instead:
```
Autoloading Some\MixedCase
Class "Some\MixedCase" does not exist
```


### PHP Version

```plain
master
```

### Operating System

_No response_