SimpleDB::select does not deserialize the Items list even though the response XML is valid.

### Describe the bug

SimpleDB::Select does not deserialize the Items list even though the response XML is valid.

NextToken is parsed correctly, but Items is always missing from the resulting Aws\Result.

# Environment

* aws/aws-sdk-php-v3-bridge: 0.4.0
* AWS SDK for PHP: 3.387.2
* PHP: 8.2.31

### Regression Issue

- [ ] Select this option if this issue appears to be a regression.

### Expected Behavior

```php
[
'Items' => [
[
'Name' => 'exmaple@example.com',
'Attributes' => [
:
],
],
],
]
```

### Current Behavior

```php
[
'@metadata' => [...],
]
```

### Reproduction Steps

```php
use Aws\SimpleDb\SimpleDbClient;
$client = new SimpleDbClient([
:
]);
$result = $client->select([
'SelectExpression' => "select * from users where itemName() = 'exmaple@example.com' limit 1",
]);
var_dump($result->toArray());
```

### Possible Solution

_No response_

### Additional Information/Context

# AWS CLI

The same query executed with the AWS CLI returns the expected result.

```shell
aws sdb select \
--select-expression "select * from users where itemName() = 'exmaple@example.com' limit 1"
```

Response:
```json
{
"Items": [
{
"Name": "exmaple@example.com",
"Attributes": [
:
]
}
]
}
```
⸻

Response XML

The SDK receives the following XML (trimmed):

```xml

exmaple@example.com
...

```

The XML appears to be valid and matches the SimpleDB API documentation.

### SDK version used

0.4.0

### Environment details (OS name and version, etc.)

macOS

Start at SimpleDbClient::select and follow the response deserialization path using the supplied XML and reproduction query. Compare how NextToken and Item/Attribute elements are mapped, then verify that the resulting Aws\Result contains Items with Name and Attributes as shown in the expected behavior.

Written by the indexing model from the issue text.