nixos/treewide: Move rename.nix imports to their respective modules

A centralized list for these renames is not good because:
- It breaks disabledModules for modules that have a rename defined
- Adding/removing renames for a module means having to find them in the
central file
- Merge conflicts due to multiple people editing the central file

nixos/modules/services/mail/postgrey.nix

@@ -42,6 +42,17 @@ with lib; let
   };
 
 in {
+  imports = [
+    (mkMergedOptionModule [ [ "services" "postgrey" "inetAddr" ] [ "services" "postgrey" "inetPort" ] ] [ "services" "postgrey" "socket" ] (config: let
+        value = p: getAttrFromPath p config;
+        inetAddr = [ "services" "postgrey" "inetAddr" ];
+        inetPort = [ "services" "postgrey" "inetPort" ];
+      in
+        if value inetAddr == null
+        then { path = "/run/postgrey.sock"; }
+        else { addr = value inetAddr; port = value inetPort; }
+    ))
+  ];
 
   options = {
     services.postgrey = with types; {