feat: Add environment variables to authenticate to registry.gitlab.com (!1178) · Merge requests · GitLab.com / GitLab Infrastructure Team / common-ci-tasks

What

Adds environment variables to the Renovate Bot CI pipeline to authenticate to registry.gitlab.com to pull private images.

This change allows renovate jobs to check versioning of container images in private registries, since this is treated separately from GitLab API calls under the hood. Example failure here: https://gitlab.com/gitlab-com/gl-infra/gitlab-dedicated/instrumentor/-/jobs/11773758409#L428