### 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_
replication_config = {
            "Role": role_arn,
            "Rules": [
                {
                    "ID": "rtc",
                    "Priority": 0,
                    "Filter": {},
                    "Status": "Disabled",
                    "Destination": {
                        "Bucket": "arn:aws:s3:::does-not-exist",
                        "StorageClass": "STANDARD",
                        "ReplicationTime": {"Status": "Enabled", "Time": {"Minutes": 15}},
                        "Metrics": {"Status": "Enabled", "EventThreshold": {"Minutes": 15}},
                    },
                    "DeleteMarkerReplication": {"Status": "Disabled"},
                }
            ],
        }
        with pytest.raises(ClientError) as e:
            aws_client.s3.put_bucket_replication(
                ReplicationConfiguration=replication_config, Bucket=bucket_src
            )
        snapshot.match("expected_error_dest_does_not_exist", e.value.response)
        # set 
        replication_config["Rules"][0]["Destination"]["Bucket"] = f"arn:aws:s3:::{bucket_dst}"
        with pytest.raises(ClientError) as e:
            aws_client.s3.put_bucket_replication(
                ReplicationConfiguration=replication_config, Bucket=bucket_src
            )
        snapshot.match("expected_error_dest_versioning_disabled", e.value.response)