Add cold storage to the open search module

[jackstockley89]

Background

There isnt a option to create cold storage option when creating open search cluster

Proposed user journey

Add parameter to the terraform module to allow creation to cold storage Check for retention period and add parameters to configure the retention period

Approach

1. add parameter in module of a. branch https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/opensearch_domain#cold_storage_options
2. test if cold storage is created in terraform from this branch, using terraform plan and apply if necessary
3. update examples to show how to to use this in the module
4. CP to define set policy for retention

Which part of the user docs does this impact

1. Repository Examples and README.md

Definition of done

• [ ] readme has been updated
• [ ] another team member has reviewed

Reference

How to write good user stories

[pwyborn]

This ticket completed - that was blocking @jackstockley89 Fix ISM Policy for cp-live-modsec-audit Opensearch#4578 https://logs.cloud-platform.service.justice.gov.uk/_dashboards/app/opensearch_index_management_dashboards#/cold-indices