This adapts the remaining chart cluster-components to install the priorities.
Note that as mentioned in comments, some deployments are not installing their priority (alertmanager, cert-manager, prometheus). within minikube. Even though, they do reference the means to install the priority (top-level key "priorityClassName"). Only blackbox-exporter behaved as documented. As does our templates deployment too (alertmanager-irc-relay).
This also realigns the differents charts (swh, software-stories) so they install their own priority classes (instead of having them centrally installed by the chart cluster-components).