Adds pagination for GAR list page

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

...stries/google_artifact_registry/components/list/table.vue

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

...ql/queries/get_artifact_registry_repository.query.graphql

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

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

.../projects/google_cloud_platform/artifact_registry_spec.rb

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

...es/google_artifact_registry/components/list/table_spec.js

...ages_and_registries/google_artifact_registry/mock_data.js

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