### 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_
metric_name = "metric-%s" % short_uid()
        namespace = "namespace-%s" % short_uid()
        
        data = [
            {
                "MetricName": metric_name,
                "Dimensions": [{"Name": "foo", "Value": "bar"}],
                "Timestamp": datetime(2019, 1, 3, tzinfo=tzutc()),
                "Unit": "Seconds",
            }
        ]
        rs = cloudwatch_client.put_metric_data(Namespace=namespace, MetricData=data)
        assert 200 == rs["ResponseMetadata"]["HTTPStatusCode"]
        
        rs = cloudwatch_client.get_metric_statistics(
            Namespace=namespace,
            MetricName=metric_name,
            StartTime=datetime(2019, 1, 1),
            EndTime=datetime(2019, 1, 10),
            Period=120,
            Statistics=["Average"],
        )
        assert metric_name == rs["Label"]
        assert 1 == len(rs["Datapoints"])
        assert data[0]["Timestamp"] == rs["Datapoints"][0]["Timestamp"]
        rs = cloudwatch_client.list_metrics(Namespace=namespace, MetricName=metric_name)
        assert 1 == len(rs["Metrics"])
        assert namespace == rs["Metrics"][0]["Namespace"]
    def test_put_metric_data_gzip(self, cloudwatch_client):