convert firewall service to new serviceDefn

this is a bit kludgey with dependencies, need to
come back and look at that

modules/firewall/service.nix

@@ -4,20 +4,11 @@
 , firewallgen
 , nftables
 }:
+{ ruleset }:
 let
   inherit (liminix.services) oneshot;
   inherit (liminix.lib) typeChecked;
   inherit (lib) mkOption types;
-  t = {
-    ruleset = mkOption {
-      type = types.anything;         # we could usefully define this more tightly
-      description = "firewall ruleset";
-    };
-  };
-in
-params:
-let
-  inherit (typeChecked "firewall" t params) ruleset;
   script = firewallgen "firewall.nft" ruleset;
 in oneshot {
   name = "firewall";