draft: merge cluster-configuration chart into this repo

This pulls the history of the cluster-configuration directory of swh-charts into a subdirectory of argocd-configuration, then updates the cluster-configuration ApplicationSet to use the local chart directly.

This will help us migrate the cluster-configuration chart-of-apps to ApplicationSets, if we want to do that.

Reproducer:

cd $(mktemp -d)
git clone https://gitlab.softwareheritage.org/swh/infra/ci-cd/swh-charts.git tmp-cluster-configuration
cd tmp-cluster-configuration
git filter-repo --path cluster-configuration --path-rename cluster-configuration/:argocd-configuration/chart/
cd ..
git clone https://gitlab.softwareheritage.org/swh/infra/ci-cd/k8s-clusters-conf.git
cd k8s-clusters-conf
git checkout -b wip/merge-cc-charts
git remote add swh-charts ../tmp-cluster-configuration
git fetch swh-charts
git merge --allow-unrelated-histories swh-charts/production