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

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

bootstrap/vars/addons.sample.yaml

@@ -4,31 +4,31 @@
 #
 
 # https://gethomepage.dev
-homepage:
+addon_homepage:
   enabled: false
 
 # https://github.com/grafana/grafana
-grafana:
+addon_grafana:
   enabled: false
   # password: # password for `admin` user
 
 # https://github.com/prometheus-community/helm-charts/tree/main/charts/kube-prometheus-stack
-kube_prometheus_stack:
+addon_kube_prometheus_stack:
   enabled: false
 
 # https://github.com/kubernetes/dashboard
-kubernetes_dashboard:
+addon_kubernetes_dashboard:
   enabled: false
   # Password can be obtained by running the following command once it is deployed:
   # kubectl -n monitoring get secret kubernetes-dashboard -o jsonpath='{.data.token}' | base64 -d
 
 # https://github.com/weaveworks/weave-gitops
-weave_gitops:
+addon_weave_gitops:
   enabled: false
   # password: # password for `admin` user
 
 # https://github.com/kubernetes-csi/csi-driver-nfs
-csi_driver_nfs:
+addon_csi_driver_nfs:
   enabled: false
   storage_class:
     # - name:   # name of the storage class (must match [a-z0-9-]+)
@@ -37,7 +37,7 @@ csi_driver_nfs:
     # ...
 
 # https://github.com/kubernetes-csi/csi-driver-smb
-csi_driver_smb:
+addon_csi_driver_smb:
   enabled: false
   storage_class:
     # - name:      # name of the storage class (must match [a-z0-9-]+)
@@ -53,7 +53,7 @@ csi_driver_smb:
     # ...
 
 # https://github.com/rancher/system-upgrade-controller
-system_upgrade_controller:
+addon_system_upgrade_controller:
   # IMPORTANT: Only enable this if you also track the version of k3s in the
   # ansible configuration files. Running ansible against an already provisioned
   # cluster with this enabled might cause your cluster to be downgraded.
@@ -61,23 +61,23 @@ system_upgrade_controller:
   enabled: false
 
 # https://github.com/morphy2k/rss-forwarder
-discord_template_notifier:
+addon_discord_template_notifier:
   # Will post commits from the template repository to the specified discord channel
   # so it's easier to keep track of changes.
   enabled: false
   webhook_url: # Discord webhook url
 
 # https://github.com/backube/volsync
-volsync:
+addon_volsync:
   enabled: false
 
 # https://github.com/XenitAB/spegel
-spegel:
+addon_spegel:
   # Note: This only applies to k0s at the moment
   enabled: false
 
 # https://github.com/longhorn/longhorn
-longhorn:
+addon_longhorn:
   # IMPORTANT: Only enable this if you have 3 or more nodes in your cluster
   # and you have enough IOPS on disk to support the number of replicas.
   # Longhorn is currently unsupported in Talos