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/talos/talconfig.yaml.j2

@@ -77,7 +77,7 @@ controlPlane:
               [plugins."io.containerd.grpc.v1.cri"]
                 enable_unprivileged_ports = true
                 enable_unprivileged_icmp = true
-              #% if spegel.enabled %#
+              #% if addon_spegel.enabled %#
               [plugins."io.containerd.grpc.v1.cri".containerd]
                 discard_unpacked_layers = false
               [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc]