### 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_
key = "my-key"
        aws_client.s3.put_(Bucket=s3_bucket, Key=key, Body=b"abcdefgh")
        with pytest.raises(ClientError) as e:
            aws_client.s3.get_(Bucket=s3_bucket, Key=key, Range="bytes=1024-4096")
        snapshot.match("exc", e.value.response)
    @markers.aws.validated
    def test_range_key_not_exists(self, s3_bucket, snapshot, aws_client):
        key = "my-key"
        with pytest.raises(ClientError) as e:
            aws_client.s3.get_(Bucket=s3_bucket, Key=key, Range="bytes=1024-4096")
        snapshot.match("exc", e.value.response)
    @markers.aws.validated
    def test_create_bucket_via_host_name(self, s3_vhost_client, aws_client):
        # TO
        # ht
        bucket_name = f"test-{short_uid()}"
        try:
            response = s3_vhost_client.create_bucket(
                Bucket=bucket_name,
                CreateBucketConfiguration={"LocationConstraint": "eu-central-1"},
            )
            assert "Location" in response
            assert response["ResponseMetadata"]["HTTPStatusCode"] == 200
            response = s3_vhost_client.get_bucket_location(Bucket=bucket_name)
            assert response["ResponseMetadata"]["HTTPStatusCode"] == 200
            assert response["LocationConstraint"] == "eu-central-1"
        finally:
            s3_vhost_client.delete_bucket(Bucket=bucket_name)
    @markers.aws.validated
    def test_put_and_get_bucket_policy(self, s3_bucket, snapshot, aws_client, allow_bucket_acl):