[FEATURE] Add custom IAM policies and security groups for head and compute nodes

[cartalla]

Is your feature request related to a problem? Please describe.

Customer needs to access custom S3 bucket to configure compute nodes to run jobs and they need a custom IAM policy to allow the access.

Describe the solution you'd like

Create config file option to pass through to IAM policies to ParallelCluster config for head and compute nodes.

ParallelCluster also allows additional security groups. There is an outstanding issue about limits for submitter security groups. I think that the solution is to create the security groups for submitter access outside of the cluster and pass the additional security groups for the compute and head nodes in the config file. The the security group relationships can be set up and then the security groups passed into the config.