### 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_
# will 
        response_vhost = .get(_bucket_url_vhost(bucket_name).replace("https://", "http://"))
        content_vhost = response_vhost.content.decode("utf-8")
        assert "<Key>my-content</Key>" in content_vhost
        # TODO 
        # asse
        assert "<Size>9</Size>" in content_vhost
        snapshot.match("request_vhost_url_content", content_vhost)
        # TODO 
        snapshot.match("request_vhost_headers", dict(response_vhost.headers))
        response_path_s = .get(_bucket_url(bucket_name))
        content_path_s = response_path_s.content.decode("utf-8")
        assert "<Key>my-content</Key>" in content_path_s
        # TODO 
        # asse
        assert "<Size>9</Size>" in content_path_s
        snapshot.match("request_path_url_content", content_path_s)
        snapshot.match("request_path_headers", dict(response_path_s.headers))
        assert content_vhost == content_path_s
    @markers.aws.validated
    @markers.snapshot.skip_snapshot_verify(
        condition=is_v2_provider,
        paths=[
            "$..ServerSideEncryption",
            "$..Prefix",
            "$..Marker",
            "$..NextMarker",
        ],
    )
    def test_s3_put_more_than_1000_items(self, s3_bucket, snapshot, aws_client):