Move Dependency Firewall to Supply Chain Security and add Artifact Registry category

Summary

This MR makes two key changes to the product categories:

1. Move Dependency Firewall to Software Supply Chain Security

• categories.yml: Changed dependency_firewall stage from package to software_supply_chain_security and updated its direction URL
• stages.yml: Moved dependency_firewall from the container_registry group (under package stage) to the pipeline_security group (under software_supply_chain_security stage)

This better aligns the Dependency Firewall with the supply chain security mission, alongside related categories like artifact_security and secrets_management.

2. Add new Artifact Registry category

• categories.yml: Added new artifact_registry category under the package stage, focused on the new add-on SKU for the artifact management use case
• stages.yml: Added artifact_registry to the container_registry group under the package stage