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/storage/volsync/app/helmrelease.yaml.j2

@@ -1,4 +1,4 @@
-#% if volsync|default({}) and volsync.enabled|default(false) %#
+#% if addon_volsync.enabled %#
 ---
 apiVersion: helm.toolkit.fluxcd.io/v2beta2
 kind: HelmRelease

bootstrap/templates/kubernetes/apps/storage/volsync/app/kustomization.yaml.j2

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

bootstrap/templates/kubernetes/apps/storage/volsync/app/prometheusrule.yaml.j2

@@ -1,4 +1,4 @@
-#% if volsync|default({}) and volsync.enabled|default(false) %#
+#% if addon_volsync.enabled %#
 ---
 apiVersion: monitoring.coreos.com/v1
 kind: PrometheusRule