### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

- Localstack fails with HTTP 500, error code "InternalError", message "not enough values to unpack (expected 2, got 1)" when `CopySource` is an invalid string for `copy_object` API.

### Expected Behavior

- For the same API `copy_object`, the cloud fails with HTTP 400, error code "InvalidArgument".
- Localstack should handle invalid `CopySource` i.e., it is a dictionary with one value or an invalid string not adhering to "{bucket}/{key}" format.

### 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

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    botoclient.copy_object(CopySource="Invalid_random_string", Bucket="test_bucket", Key=key) 


 test_bucket is a valid bucket.  

### Environment

```markdown
- OS: Ubuntu 22.04.2 LTS
- LocalStack: 2.1.0
- boto3: 1.28.6
```


### Anything else?

_No response_
list_inv_configs_after_del = aws_client.s3.list_bucket_inventory_configurations(
            Bucket=src_bucket
        )
        snapshot.match("list-inventory-config-after-del", list_inv_configs_after_del)
        with pytest.raises(ClientError) as e:
            aws_client.s3.get_bucket_inventory_configuration(
                Bucket=src_bucket,
                Id=inventory_config["Id"],
            )
        snapshot.match("get-nonexistent-inv-config", e.value.response)
    @markers.aws.validated
    def test_s3_put_inventory_report_exceptions(self, aws_client, s3_create_bucket, snapshot):
        snapshot.add_transformer(snapshot.transform.resource_name())
        src_bucket = s3_create_bucket()
        dest_bucket = s3_create_bucket()
        config_id = "test-inventory"
        def _get_config():
            return {
                "Id": config_id,
                "Destination": {
                    "S3BucketDestination": {
                        "Bucket": f"arn:aws:s3:::{dest_bucket}",
                        "Format": "CSV",
                    }
                },
                "IsEnabled": True,
                "IncludedVersions": "All",
                "Schedule": {"Frequency": "Daily"},
            }
        def _put_bucket_inventory_configuration(inventory_configuration):