Adds header component to google artifact registry list page

...javascripts/vue_shared/components/registry/title_area.vue

...tries/google_artifact_registry/components/list/header.vue

..._and_registries/google_artifact_registry/graphql/index.js

...fact_registry/graphql/queries/get_artifacts.query.graphql

..._registries/google_artifact_registry/graphql/resolvers.js

...packages_and_registries/google_artifact_registry/index.js

...es_and_registries/google_artifact_registry/pages/list.vue

...projects/google_cloud_platform/artifact_registry/index.js

...s/google_cloud_platform/artifact_registry/index.html.haml

.../projects/google_cloud_platform/artifact_registry_spec.rb

...s/google_artifact_registry/components/list/header_spec.js

...ages_and_registries/google_artifact_registry/mock_data.js

...nd_registries/google_artifact_registry/pages/list_spec.js

locale/gitlab.pot