### 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_
response = .get(bucket_vhost_url)
        assert response.status_code == 404
        bucket_url = _bucket_url(bucket_name, region="us-west-2")
        assert "us-west-2" in bucket_url
        response = .get(bucket_url)
        assert response.status_code == 404
    @markers.aws.validated
    @markers.snapshot.skip_snapshot_verify(
        paths=["$..x-amz-access-point-alias", "$..x-amz-id-2", "$..AccessPointAlias"],
    )
    def test_create_bucket_head_bucket(
        self, aws_client_factory, snapshot, aws_client, secondary_region_name
    ):
        snapshot.add_transformer(snapshot.transform.s3_api())
        bucket_1 = f"my-bucket-1{short_uid()}"
        bucket_2 = f"my-bucket-2{short_uid()}"
        snapshot.add_transformers_list(
            [
                snapshot.transform.regex(rf"{bucket_1}", "<bucket-name:1>"),
                snapshot.transform.regex(rf"{bucket_2}", "<bucket-name:2>"),
                snapshot.transform.key_value("x-amz-id-2", reference_replacement=False),
                snapshot.transform.key_value("x-amz-request-id", reference_replacement=False),
                snapshot.transform.regex(r"s3\.amazonaws\.com", "<host>"),
                snapshot.transform.regex(r"s3\.localhost\.localstack\.cloud:4566", "<host>"),
                snapshot.transform.regex(r"s3\.localhost\.localstack\.cloud:443", "<host>"),
                snapshot.transform.key_value("x-amz-bucket-region"),
            ]
        )
        try:
            client = aws_client_factory(region_name="us-east-1").s3