Adds gcloud for all x86 platforms

This adds python3 and gcloud for all x86 Ubuntu Docker files. This targets Ubuntu because I am working under the assumption that all auto-deploys will be using the Ubuntu image (to avoid adding it everywhere).

Part of https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/16340, this adds the gcloud dependency so it can be used for uploading package artifacts to a GCP bucket for autodeploy.