### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

The use case I have in mind is to run Node 16.x Lambdas - the default container registry is `lambci/lambda` which is effectively abandoned. [Not even Node 14.x has been published](https://github.com/lambci/docker-lambda/pull/330). However, switching the registry over to [`amazon/aws-lambda-nodejs`](https://hub.docker.com/r/amazon/aws-lambda-nodejs) still fails to pull the container, since localstack is looking for the tag `nodejs16.x`. I'd like to be able to specify that if the runtime is `nodejs16.x` it just looks for tag `16`.

### 🧑‍💻 Implementation

_No response_

### Anything else?

_No response_
if arn:
            self.function_invoke_times.pop(arn, None)
            return self.destroy_docker_container(arn)
        self.function_invoke_times = {}
        return self.destroy_existing_docker_containers()
    def prime_docker_container(
        self,
        lambda_function: LambdaFunction,
        env_vars: Dict,
        lambda_cwd: str,
        docker_flags: str = None,
    ):
        """
        Prepares a persistent docker container for a specific function.
        :param lambda_function: The Details of the lambda function.
        :param env_vars: The environment variables for the lambda.
        :param lambda_cwd: The local directory containing the code for the lambda function.
        :return: ContainerInfo class containing the container name and default entry point.
        """
        with self.docker_container_lock:
            
            func_arn = lambda_function.arn()
            container_name = self.get_container_name(func_arn)
            status = self.get_docker_container_status(func_arn)
            LOG.debug('Priming Docker container (status "%s"): %s', status, container_name)
            docker_image = Util.docker_image_for_lambda(lambda_function)
            
            if status < 1: