### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

PutMetricData with arrays of values does not work properly. Zero values seem to be published. PutMetricData with a single value works as expected. This happens to both CLI and SDK.

### Expected Behavior

PutMetricData with arrays of values should work as publishing a single value.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack:1.2.0

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)
```
awslocal cloudwatch put-metric-data --namespace test --metric-data MetricName=TestCounter,Values=10,1,Counts=1,1
awslocal cloudwatch get-metric-statistics --namespace test --metric-name TestCounter --statistics Maximum --period 60 --start-time 2022-11-9T00:00:00Z --end-time 2022-11-11T00:00:00Z
{
    "Label": "TestCounter",
    "Datapoints": [
        {
            "Timestamp": "2022-11-09T23:25:10+00:00",
            "Maximum": 0.0,
            "ExtendedStatistics": {}
        },
        {
            "Timestamp": "2022-11-09T23:27:10+00:00",
            "Maximum": 0.0,
            "ExtendedStatistics": {}
        }
    ]
}
```



### Environment

```markdown
- OS: Mac Monterey
- LocalStack: 1.2.0
```


### Anything else?

_No response_
res = cloudwatch_client.list_metrics(Dimensions=dimensions)
            metrics = [metric["MetricName"] for metric in res["Metrics"]]
            if all(
                m in metrics
                for m in ["NumberOfMessagesSent", "SentMessageSize", "NumberOfEmptyReceives"]
            ):
                res = cloudwatch_client.get_metric_data(
                    MetricDataQueries=[sent, sent_size, empty],
                    StartTime=datetime.utcnow() - timedelta(hours=1),
                    EndTime=datetime.utcnow(),
                )
                
                if (
                    res["MetricDataResults"][0]["Values"]
                    and res["MetricDataResults"][1]["Values"]
                    and res["MetricDataResults"][2]["Values"]
                ):
                    return True
            return False
        assert poll_condition(lambda: contains_sent_messages_metrics(), interval=1, timeout=120)
        response = cloudwatch_client.get_metric_data(
            MetricDataQueries=[sent, sent_size, empty],
            StartTime=datetime.utcnow() - timedelta(hours=1),
            EndTime=datetime.utcnow(),
        )
        snapshot.match("get_metric_data", response)
        
        sqs_messages = sqs_client.receive_message(QueueUrl=sqs_url)["Messages"]