### 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.resource_name())
        src_bucket = s3_create_bucket()
        dest_bucket = s3_create_bucket()
        policy = {
            "Version": "2012-10-17",
            "Statement": [
                {
                    "Sid": "InventoryPolicy",
                    "Effect": "Allow",
                    "Principal": {"Service": "s3.amazonaws.com"},
                    "Action": "s3:Pu",
                    "Resource": [f"arn:aws:s3:::{dest_bucket}/*"],
                    "Condition": {
                        "ArnLike": {"aws:SourceArn": f"arn:aws:s3:::{src_bucket}"},
                    },
                },
            ],
        }
        aws_client.s3.put_bucket_policy(Bucket=dest_bucket, Policy=json.dumps(policy))
        inventory_config = {