feat: rename addon vars to addon_ prefix and simplify logic in jinja templates (#1216)

Signed-off-by: Devin Buhl <devin@buhl.casa>

bootstrap/templates/kubernetes/apps/observability/kustomization.yaml.j2

@@ -3,12 +3,12 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - ./namespace.yaml
-  #% if grafana|default({}) and grafana.enabled|default(false) %#
+  #% if addon_grafana.enabled %#
   - ./grafana/ks.yaml
   #% endif %#
-  #% if kube_prometheus_stack|default({}) and kube_prometheus_stack.enabled|default(false) %#
+  #% if addon_kube_prometheus_stack.enabled %#
   - ./kube-prometheus-stack/ks.yaml
   #% endif %#
-  #% if kubernetes_dashboard|default({}) and kubernetes_dashboard.enabled|default(false) %#
+  #% if addon_kubernetes_dashboard.enabled %#
   - ./kubernetes-dashboard/ks.yaml
   #% endif %#