[New Feature]: Add in `c6id` EC2 instance types to be used by both the CWL DAG and modular CWL DAGs

[nikki-t]

Integrate the following instance types:

c6id.xlarge
c6id.2xlarge
c6id.4xlarge

1. Modify unity_sps_utils to include new instance types.
2. Add c6id to variables.tf

[nikki-t]

Also need to update node user data script to include "6id" instance family.