Add support to the Artifact Registry CI template for code repositories with multiple apps

Some repositories (e.g. the malware scanner apps repository) contain multiple "sub-apps" in order to ease integration testing in the case where the individual apps are quite small. The auto-devops/artifact-registry.yml CI template currently doesn't support this use case well as the name assigned to images pushed to Artifact Registry are always based on the GitLab project name.

This issue covers adding a ARTIFACT_REGISTRY_IMAGE_NAME variable to the auto-devops/artifact-registry.yml CI template in order to override the name assigned to images pushed to Artifact Registry.