plugins/telescope: refactor mkExtension

Allow importing `mkExtension` without needing to supply any
dependencies.

All dependencies can be accessed via module args anyway.

plugins/by-name/telescope/extensions/_mk-extension.nix

@@ -0,0 +1,85 @@
+{
+  name,
+  package,
+  extensionName ? name,
+  settingsOptions ? { },
+  settingsExample ? null,
+  extraOptions ? { },
+  imports ? [ ],
+  optionsRenamedToSettings ? [ ],
+  extraConfig ? cfg: { },
+}:
+let
+  getPluginAttr = attrs: attrs.plugins.telescope.extensions.${name};
+
+  renameModule =
+    { lib, ... }:
+    {
+      # TODO remove this once all deprecation warnings will have been removed.
+      imports =
+        let
+          basePluginPath = [
+            "plugins"
+            "telescope"
+            "extensions"
+            name
+          ];
+          settingsPath = basePluginPath ++ [ "settings" ];
+        in
+        builtins.map (
+          option:
+          let
+            optionPath = lib.toList option;
+            optionPathSnakeCase = map lib.nixvim.toSnakeCase optionPath;
+          in
+          lib.mkRenamedOptionModule (basePluginPath ++ optionPath) (settingsPath ++ optionPathSnakeCase)
+        ) optionsRenamedToSettings;
+    };
+
+  module =
+    {
+      lib,
+      config,
+      pkgs,
+      ...
+    }:
+    let
+      cfg = getPluginAttr config;
+    in
+    {
+      options.plugins.telescope.extensions.${name} = {
+        enable = lib.mkEnableOption "the `${name}` telescope extension";
+
+        package = lib.mkPackageOption pkgs name {
+          default = [
+            "vimPlugins"
+            package
+          ];
+        };
+
+        settings = lib.nixvim.mkSettingsOption {
+          description = "settings for the `${name}` telescope extension.";
+          options = settingsOptions;
+          example = settingsExample;
+        };
+      } // extraOptions;
+
+      config = lib.mkIf cfg.enable {
+        extraPlugins = [ cfg.package ];
+
+        plugins.telescope = {
+          enabledExtensions = [ extensionName ];
+          settings.extensions.${extensionName} = cfg.settings;
+        };
+      };
+    };
+
+  extraConfigModule = { config, ... }: extraConfig (getPluginAttr config);
+in
+{
+  imports = imports ++ [
+    module
+    extraConfigModule
+    renameModule
+  ];
+}