Add status conditions to all objects

[theSuess]

Kubernetes status conditions are the way to go, especially regarding automated healtchecks (see #1444).

While the new alert rule group CR already supports this, we need to implement status conditions for the remaining resources.

### Tasks
- [ ] Grafana
- [x] GrafanaFolder
- [x] GrafanaDashboard
- [ ] GrafanaDatasource