### 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_
"Unit": "Percent",
            "Period": 300,
            "EvaluationPeriods": 2,
            "ComparisonOperator": "GreaterThanThreshold",
            "Threshold": 50.0,
            "TreatMissingData": "ignore",
            "EvaluateLowSampleCountPercentile": "",
            "Dimensions": [{"value": "i-0317828c84edbe100", "name": "InstanceId"}],
            "StatisticType": "Statistic",
            "Statistic": "AVERAGE",
        }
        try:
            
            subscription_alarm = sns_client.subscribe(
                TopicArn=topic_arn_alarm, Protocol="sqs", Endpoint=arn_queue_alarm
            )
            subscription_ok = sns_client.subscribe(
                TopicArn=topic_arn_ok, Protocol="sqs", Endpoint=arn_queue_ok
            )
            
            cloudwatch_client.put_metric_alarm(
                AlarmName=alarm_name,
                AlarmDescription=alarm_description,
                MetricName=expected_trigger["MetricName"],
                Namespace=expected_trigger["Namespace"],
                ActionsEnabled=True,
                Period=expected_trigger["Period"],
                Threshold=expected_trigger["Threshold"],
                Dimensions=[{"Name": "InstanceId", "Value": "i-0317828c84edbe100"}],
                Unit=expected_trigger["Unit"],