Kubernetes Dashboard implementation - iteration #1
### Goal (\~ 12 MRs)
1. Create a new route and a controller for the dashboard. We can use `/-/kubernetes/<agent-id>/`. Use the `read_cluster_agent` policy in order to keep the authorization consistent across different pages. - ~backend
1. Handle the state where no agent ID was provided ([design issue](https://gitlab.com/gitlab-org/gitlab/-/issues/422441)) - ~frontend
1. Handle the state where the provided agent is unavailable or cannot connect to the cluster ([design issue](https://gitlab.com/gitlab-org/gitlab/-/issues/422443)) - ~frontend
1. Add a Vue router for the workload types: Pods, Deployments, StatefulSets, ReplicaSets, DaemonSets, Jobs, and CronJobs. Each of the pages should have an empty state and a loading state - ~frontend
1. For each workload type (one by one) page render - ~frontend
* A set of single stats

* A table (**without** CPU, Memory, and Project cells for now)

* A drawer for each item with additional information (only the description tab for now)

epic