Use zone names and region names instead of indices in archetype deploy pipeline module

The terraform module deploy-pipelines uses indices instead of zone names and region names.
This can be clunky, using explicit names would be an improvement

Start by locating the Terraform module named deploy-pipelines and trace where zone and region indices are defined and consumed. Replace those index-based references with explicit zone and region names, then verify that the archetype deploy pipeline still plans and deploys correctly across its configured zones and regions.

Written by the indexing model from the issue text.