### 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_
cloudwatch_client.put_metric_data(
            Namespace="AWS/EC2",
            MetricData=[
                {
                    "MetricName": "CPUUtilization",
                    "Dimensions": [{"Name": "InstanceId", "Value": "i-46cdcd06a11207ab3"}],
                    "Value": 15,
                }
            ],
        )
        
        results = cloudwatch_client.list_metrics(Namespace="AWS/EC2")["Metrics"]
        assert 2 == len(results)
    def test_put_metric_alarm_escape_character(self, cloudwatch_client):
        cloudwatch_client.put_metric_alarm(
            AlarmName="cpu-mon",
            AlarmDescription="<",
            MetricName="CPUUtilization-2",
            Namespace="AWS/EC2",
            Statistic="Sum",
            Period=600,
            Threshold=1,
            ComparisonOperator="GreaterThanThreshold",
            EvaluationPeriods=1,
            AlarmActions=["arn:aws:sns:us-east-1:111122223333:MyTopic"],
        )
        result = cloudwatch_client.describe_alarms()
        assert result.get("MetricAlarms")[0]["AlarmDescription"] == "<"
        cloudwatch_client.delete_alarms(AlarmNames=["cpu-mon"])
    def test_set_alarm(