treewide: use attrs instead of list for types.loaOf options

nixos/modules/security/pam.nix

@@ -475,9 +475,9 @@ let
 
   motd = pkgs.writeText "motd" config.users.motd;
 
-  makePAMService = pamService:
-    { source = pkgs.writeText "${pamService.name}.pam" pamService.text;
-      target = "pam.d/${pamService.name}";
+  makePAMService = name: service:
+    { name = "pam.d/${name}";
+      value.source = pkgs.writeText "${name}.pam" service.text;
     };
 
 in
@@ -760,8 +760,7 @@ in
       };
     };
 
-    environment.etc =
-      mapAttrsToList (n: v: makePAMService v) config.security.pam.services;
+    environment.etc = mapAttrs' makePAMService config.security.pam.services;
 
     security.pam.services =
       { other.text =