Move Docker images from Container Registry to Artifact Registry

`cloudbuild.yaml` currently pushes Docker images to Google Cloud Registry (GCR). However, as highlighted in the [Google Cloud documentation](https://cloud.google.com/artifact-registry/docs/transition/transition-from-gcr):

> Artifact Registry is the recommended service for container image storage and management on Google Cloud. As a fully-managed service with support for both container images and non-container artifacts, Artifact Registry extends the capabilities of Container Registry.

Transition from Cloud Registry to Artifact Registry by updating `cloudbuild.yaml` (and everything related in the build/tag/deploy process, like docs, Terraform scripts and Makefile targets).