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/monitoring/prometheus/alertmanager.nix

@@ -27,6 +27,15 @@ let
       "--log.format ${cfg.logFormat}"
   );
 in {
+  imports = [
+    (mkRemovedOptionModule [ "services" "prometheus" "alertmanager" "user" ] "The alertmanager service is now using systemd's DynamicUser mechanism which obviates a user setting.")
+    (mkRemovedOptionModule [ "services" "prometheus" "alertmanager" "group" ] "The alertmanager service is now using systemd's DynamicUser mechanism which obviates a group setting.")
+    (mkRemovedOptionModule [ "services" "prometheus" "alertmanagerURL" ] ''
+      Due to incompatibility, the alertmanagerURL option has been removed,
+      please use 'services.prometheus2.alertmanagers' instead.
+    '')
+  ];
+
   options = {
     services.prometheus.alertmanager = {
       enable = mkEnableOption "Prometheus Alertmanager";

nixos/modules/services/monitoring/prometheus/default.nix

@@ -464,6 +464,11 @@ let
   };
 
 in {
+
+  imports = [
+    (mkRenamedOptionModule [ "services" "prometheus2" ] [ "services" "prometheus" ])
+  ];
+
   options.services.prometheus = {
 
     enable = mkOption {

nixos/modules/services/monitoring/prometheus/exporters.nix

@@ -160,6 +160,24 @@ let
   };
 in
 {
+
+  imports = (lib.forEach [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
+                   "jsonExporter" "minioExporter" "nginxExporter" "nodeExporter"
+                   "snmpExporter" "unifiExporter" "varnishExporter" ]
+       (opt: lib.mkRemovedOptionModule [ "services" "prometheus" "${opt}" ] ''
+         The prometheus exporters are now configured using `services.prometheus.exporters'.
+         See the 18.03 release notes for more information.
+       '' ))
+
+    ++ (lib.forEach [ "enable" "substitutions" "preset" ]
+       (opt: lib.mkRemovedOptionModule [ "fonts" "fontconfig" "ultimate" "${opt}" ] ''
+         The fonts.fontconfig.ultimate module and configuration is obsolete.
+         The repository has since been archived and activity has ceased.
+         https://github.com/bohoomil/fontconfig-ultimate/issues/171.
+         No action should be needed for font configuration, as the fonts.fontconfig
+         module is already used by default.
+       '' ));
+
   options.services.prometheus.exporters = mkOption {
     type = types.submodule {
       options = (mkSubModules);