### 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_
UploadId=upload_id,
                MultipartUpload={"Parts": [{"ETag": part_etag, "PartNumber": 2}]},
            )
        snapshot.match("complete-exc-wrong-part-number", e.value.response)
        with pytest.raises(ClientError) as e:
            wrong_etag = "d41d8cd98f00b204e9800998ecf8427e"
            aws_client.s3.complete_multipart_upload(
                Bucket=s3_bucket,
                Key=key_name,
                UploadId=upload_id,
                MultipartUpload={"Parts": [{"ETag": wrong_etag, "PartNumber": 1}]},
            )
        snapshot.match("complete-exc-wrong-etag", e.value.response)
    @markers.aws.validated
    @markers.snapshot.skip_snapshot_verify(
        condition=is_v2_provider,
        paths=["$..ServerSideEncryption"],
    )
    def test_put_and_get__with_hash_prefix(self, s3_bucket, snapshot, aws_client):
        snapshot.add_transformer(snapshot.transform.s3_api())
        key_name = "#key-with-hash-prefix"
        content = b"test 123"
        response = aws_client.s3.put_(Bucket=s3_bucket, Key=key_name, Body=content)
        assert response["ResponseMetadata"]["HTTPStatusCode"] == 200
        snapshot.match("put-", response)
        response = aws_client.s3.get_(Bucket=s3_bucket, Key=key_name)
        snapshot.match("get-", response)
        assert response["Body"].read() == content
    @markers.aws.validated
    def test_invalid_range_error(self, s3_bucket, snapshot, aws_client):