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/kube-prometheus-stack/app/helmrelease.yaml.j2

@@ -1,4 +1,4 @@
-#% if kube_prometheus_stack|default({}) and kube_prometheus_stack.enabled|default(false) %#
+#% if addon_kube_prometheus_stack.enabled %#
 ---
 apiVersion: helm.toolkit.fluxcd.io/v2beta2
 kind: HelmRelease
@@ -121,7 +121,7 @@ spec:
       ingress:
         enabled: true
         ingressClassName: internal
-        #% if homepage|default({}) and homepage.enabled|default(false) %#
+        #% if addon_homepage.enabled %#
         annotations:
           gethomepage.dev/enabled: "true"
           gethomepage.dev/icon: prometheus.png

bootstrap/templates/kubernetes/apps/observability/kube-prometheus-stack/app/kustomization.yaml.j2

@@ -1,4 +1,4 @@
-#% if kube_prometheus_stack|default({}) and kube_prometheus_stack.enabled|default(false) %#
+#% if addon_kube_prometheus_stack.enabled %#
 ---
 apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization

bootstrap/templates/kubernetes/apps/observability/kube-prometheus-stack/ks.yaml.j2

@@ -1,4 +1,4 @@
-#% if kube_prometheus_stack|default({}) and kube_prometheus_stack.enabled|default(false) %#
+#% if addon_kube_prometheus_stack.enabled %#
 ---
 apiVersion: kustomize.toolkit.fluxcd.io/v1
 kind: Kustomization