### 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_
snapshot.add_transformer(
            [
                snapshot.transform.key_value(
                    "Bucket", reference_replacement=False, value_replacement="<bucket>"
                ),
            ]
        )
        bucket = s3_create_bucket()
        analytics_bucket = s3_create_bucket()
        analytics_bucket_arn = f"arn:aws:s3:::{analytics_bucket}"
        storage_analysis = {
            "Id": "config_with_storage_analysis_1",
            "Filter": {
                "Prefix": "test_ls",
            },
            "StorageClassAnalysis": {
                "DataExport": {
                    "OutputSchemaVersion": "V_1",
                    "Destination": {
                        "S3BucketDestination": {
                            "Format": "CSV",
                            "Bucket": analytics_bucket_arn,
                            "Prefix": "test",
                        }
                    },
                }
            },