Draft: Add integration for artifact registry service

What does this merge request do and why?

⚠️ This is part of a PoC that includes a Go based version of the artifact registry (from https://gitlab.com/jdrpereira/artifact-registry-poc). The final tech stack is being discussed in gitlab-com/content-sites/handbook!18455 (merged). This MR is a draft and may need to be revised once the former is closed.

Add component definition, service class, config template, bootstrap script, Makefile targets, and version file for the artifact registry microservice.

Register ports 9080 (HTTP) and 9180 (metrics), add repository URL to config, and wire into setup/update/reconfigure/postgresql-seed task chains.

Service is opt-in via artifact_registry.enabled: true in gdk.yml.

How to set up and validate locally

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This MR references an issue describing the change.
• This change is backward compatible. If not, include steps to communicate to users.
• Tests added for new functionality. If not, raise an issue to follow-up.
• Observability added/updated (logging, metrics, tracing).
• Documentation added/updated.
• Announcement added for notable changes.
• gdk doctor test added.