Revert "Add nixosSubmodule option type"

Moving recent types work to a separate branch for now

This reverts commit ca1c5cfa8f.

lib/types.nix

@@ -195,25 +195,6 @@ rec {
             args = { name = ""; }; }).options;
       };
 
-    nixosSubmodule = nixos: args: mkOptionType rec {
-      name = "submodule containing a NixOS config";
-      check = x: isAttrs x || isFunction x;
-      merge = loc: defs:
-        let
-          coerce = def: if isFunction def then def else { config = def; };
-        in (import (nixos + "/lib/eval-config.nix") (args // {
-          modules = (args.modules or []) ++
-            map (def: { _file = def.file; imports = [(coerce def.value)]; }) defs;
-
-          prefix = loc;
-        })).config;
-      getSubOptions = prefix: (import (nixos + "/lib/eval-config.nix") (args // {
-        modules = (args.modules or []);
-
-        inherit prefix;
-      })).options;
-    };
-
     # Obsolete alternative to configOf.  It takes its option
     # declarations from the ‘options’ attribute of containing option
     # declaration.

nixos/modules/virtualisation/containers.nix

@@ -15,7 +15,6 @@ with pkgs.lib;
     };
 
     systemd.containers = mkOption {
-      # !!! Should probably use nixosSubmodule here
       type = types.attrsOf (types.submodule (
         { config, options, name, ... }:
         {
@@ -135,4 +134,4 @@ with pkgs.lib;
       }) config.systemd.containers;
 
   };
-}
+}