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/flux-system/kustomization.yaml.j2

@@ -4,6 +4,6 @@ kind: Kustomization
 resources:
   - ./namespace.yaml
   - ./addons/ks.yaml
-  #% if weave_gitops|default({}) and weave_gitops.enabled|default(false) %#
+  #% if addon_weave_gitops.enabled %#
   - ./weave-gitops/ks.yaml
   #% endif %#