[Backend] Add support to recreate workers on EC2 instance for active challenges

### Description

To push latest changes to active workers on EC2 instance we need to recreate the service so that it uses the latest docker image of submission worker. Currently, we recreate worker service for each challenge manually by deleting the worker and starting it again using [worker deployment script](https://github.com/Cloud-CV/EvalAI/blob/master/scripts/deployment/deploy.sh#L210) individually.

We need to add support for recreating the fargate service (i.e. delete service and create) for all active challenges in the deployment script.

Deliverables:

1. Add API calls to fetch all active challenges
2. Use the fetched challenges to recreate the workers on EC2 instance