### Description

I want to add support of a separate AWS connection for DynamoDB in `DynamoDBToS3Operator` in `apache-airflow-providers-amazon` via `aws_dynamodb_conn_id` constructor argument.



### Use case/motivation

Sometimes DynamoDB tables and S3 buckets live in different AWS accounts so to access both resources you need to assume a role in another account from one of them.
That role can be specified in AWS connection, thus we need to support two of them in this operator.

### Related issues

_No response_

### Are you willing to submit a PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

responses = [
            {
                "Items": [{"a": 1}, {"b": 2}],
                "LastEvaluatedKey": "123",
            },
            {
                "Items": [{"c": 3}],
            },
        ]
        table = MagicMock()
        table.return_value.scan.side_effect = responses
        mock_aws_dynamodb_hook.return_value.get_conn.return_value.Table = table
        s3_client = MagicMock()
        s3_client.return_value.upload_file = self.mock_upload_file
        mock_s3_hook.return_value.get_conn = s3_client
        aws_conn_id = "test-conn-id"
        dynamodb_to_s3_operator = DynamoDBToS3Operator(
            task_id="dynamodb_to_s3",
            dynamodb_table_name="airflow_rocks",
            s3_bucket_name="airflow-bucket",
            file_size=4000,
            aws_conn_id=aws_conn_id,
        )
        dynamodb_to_s3_operator.execute(context={})
        assert [{"a": 1}, {"b": 2}, {"c": 3}] == self.output_queue
        mock_s3_hook.assert_called_with(aws_conn_id=aws_conn_id)
        mock_aws_dynamodb_hook.assert_called_with(aws_conn_id=aws_conn_id)