Automatically create upgrade MRs for infrastructure components in the `k8s-mgmt/clusters` repository.

We currently lack a mechanism for upgrading infrastructure components, such as

• external-secrets (#285 (closed))
• cert-manager (#457 (closed))
• opentelemetry-collector (#289 (closed))

To do:

• Add the k8s-mgmt/clusters repository to infra-mgmt. Ensure the common_ci_tasks integration is enabled, specifically Renovate.
• Add the common-ci-tasks templates/standard.yml tempalte to .gitlab-ci.yml.
• Write a Renovate config that can upgrade the versions specified in the HelmRelease resource manifests. Preferably we match files on the kind: HelmRelease content. Failing that, we may have to enforce a naming standard for these files and match on their file name instead.

Note

There is existing automation in the k8s-mgmt/clusters repository for upgrading Flux. It's unclear whether we should use that for upgrading Flux or whether we should prefer to use Renovate instead. We'll decide this in a separate issue.