[autoscaler] Minimizing EC2 Cluster Launcher's Permissions

[annaluo676]

Ray comes with a built-in cluster launcher that deploys a Ray cluster. It launches a single head node and uses that node to launch the cluster’s worker nodes. As a result, an IAM role with appropriate permissions should be granted to the laucher. In most use cases (especially for research purposes) this is not an issue as the user has admin role. However, when the launch task is delegated to another service (e.g., a Fargate Task), we'd like to clearly define the permissions required.

Note that this role is for the launcher to launch a cluster and it's different from the role of the head node itself. As detailed in
[autoscaler] Ray Cluster Launcher on AWS | Minimizing Permissions #9327, this issue deals with ray-ec2-launcher's IAM role only. Triming down the permissions granted to ray-head-v1 and ray-worker-v1 should be a separate issue.