Feat/templatetf

[sjpb]

Use ansible cluster_* vars to template out terraform:

• Display of planned changes with interactive prompt.
• Still uses file-based inventory is still file-based.
• Supports flexible port and volume configuration on all instances.

TODO

Post caas-merge this is a bit of a mess, with tf templates both in roles/terraform and roles/cluster_infra. Probably what we want to do is:

• Update stackhpc.terraform to include the logic for interactive use from roles/terraform
• Make sure we can deploy the stackhpc environment using the roles/cluster_infra templates (this will lose some functionality, like port types)
• Add back, incrementally, functionality for port types, node groups etc.