Add simulated multi-node test

[nikhil-sk]

Description

1. Creates a simulated multi-node setup using docker bridge networking/
2. The environment variables mimic EKS+LWS setup, with one leader and one worker node.
3. The 4 instance type GPUs are split as 2 for leader, and 2 for worker, testing tp_degree=4 config.
4. Will update the test to use tp=2, and pp=2 when we have full pp degree integration.