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Having upgraded to the latest LocalStack version, I've noticed that Docker containers from Lambda executions are immediately removed when they terminate.

This was added in https://github.com/localstack/localstack/pull/1584

I can appreciate the need to clean up containers, however this feature of having them stay up is actually very useful for debugging things when they go wrong!

Would it be possible to have a flag so that when running LocalStack we can specify whether to remove containers on completion? Something like:

```
services:
  localstack:
    image: localstack/localstack:latest
    ports:
      - "4567-4593:4567-4593"
    environment:
      - SERVICES=serverless,ssm,stepfunctions
      - DOCKER_HOST=unix:///var/run/docker.sock
      - LAMBDA_EXECUTOR=docker
      - REMOVE_CONTAINERS_ON_LAMBDA_TERMINATE=true #(or false)
    volumes:
      - "${TMPDIR:-/tmp/localstack}:/tmp/localstack"
      - "/var/run/docker.sock:/var/run/docker.sock"
```

Thanks for the great work folks!
return ContainerInfo(container_name, entry_point)
    def destroy_docker_container(self, func_arn):
        """
        Stops and/or removes a docker container for a specific lambda function ARN.
        :param func_arn: The ARN of the lambda function.
        :return: None
        """
        with self.docker_container_lock:
            status = self.get_docker_container_status(func_arn)
            docker_cmd = self._docker_cmd()
            
            container_name = self.get_container_name(func_arn)
            if status == 1:
                LOG.debug('Stopping container: %s' % container_name)
                cmd = (
                    '%s stop -t0 %s'
                ) % (docker_cmd, container_name)
                LOG.debug(cmd)
                run(cmd, asynchronous=False, stderr=subprocess.PIPE, outfile=subprocess.PIPE)
                status = self.get_docker_container_status(func_arn)
            if status == -1:
                LOG.debug('Removing container: %s' % container_name)
                cmd = (
                    '%s rm %s'
                ) % (docker_cmd, container_name)
                LOG.debug(cmd)
                run(cmd, asynchronous=False, stderr=subprocess.PIPE, outfile=subprocess.PIPE)
    def get_all_container_names(self):
        """
        Returns a list of container names for lambda containers.