Add ability to not assign Public IPs on Azure

What does this MR do?

Adding setup_external_ips setting similar to existing approach GET has for GCP. When specified as false GET won't create public IPs for VMs in Azure.

module "gitlab_ref_arch_azure" {
  source = "../../modules/gitlab_ref_arch_azure"

 ...

  setup_external_ips = false

...
}

At the same time a NAT gateway will be configured to ensure continued Internet access.

Verification that 3k-rails VM uses NAT public IP for Internet access

Related issues

Closes #411 (closed)

Author's checklist

When ready for review, the Author applies the workflowready for review label and mention @gl-quality/get-maintainers:

• Merge request:
  • Corresponding Issue raised and reviewed by the GET maintainers team.
  • Merge Request Title and Description are up to date, accurate, and descriptive
  • MR targeting the appropriate branch
  • MR has a green pipeline
  • MR has no new security alerts in the widget from the Secret Detection and IaC Scan (SAST) jobs.
• Code:
  • Check the area changed works as expected. Consider testing it in different environment sizes (1k,3k,10k,etc.).
  • Documentation created/updated in the same MR.
  • If this MR adds an optional configuration - check that all permutations continue to work.
  • For Terraform changes: setup a previous version environment, then run a terraform plan with your new changes and ensure nothing will be destroyed. If anything will be destroyed and this can't be avoided please add a comment to the current MR.
• Create any follow-up issue(s) to support the new feature across other supported cloud providers or advanced configurations. Create 1 issue for each provider/configuration. Contact the Quality Enablement team if unsure.