plugins/completion: move to by-name

- Move nvim-cmp to plugins/cmp
- Move other completion plugins to plugins/by-name

plugins/completion/cmp/sources/copilot-cmp.nix

@@ -1,65 +0,0 @@
-{
-  lib,
-  helpers,
-  config,
-  ...
-}:
-with lib;
-let
-  copilot-lua-cfg = config.plugins.copilot-lua;
-  cfg = config.plugins.copilot-cmp;
-in
-{
-  options.plugins.copilot-cmp = helpers.neovim-plugin.extraOptionsOptions // {
-    event =
-      helpers.defaultNullOpts.mkListOf types.str
-        [
-          "InsertEnter"
-          "LspAttach"
-        ]
-        ''
-          Configures when the source is registered.
-          Unless you have a unique problem for your particular configuration you probably don't want
-          to touch this.
-        '';
-
-    fixPairs = helpers.defaultNullOpts.mkBool true ''
-      Suppose you have the following code: `print('h')`.
-      Copilot might try to account for the `'` and `)` and complete it with this: `print('hello`.
-
-      This is not good behavior for consistency reasons and will just end up deleting the two ending
-      characters.
-      This option fixes that.
-      Don't turn this off unless you are having problems with pairs and believe this might be
-      causing them.
-    '';
-  };
-
-  config = mkIf cfg.enable {
-    warnings =
-      optional ((!isBool copilot-lua-cfg.suggestion.enabled) || copilot-lua-cfg.suggestion.enabled) ''
-        It is recommended to disable copilot's `suggestion` module, as it can interfere with
-        completions properly appearing in copilot-cmp.
-      ''
-      ++ optional ((!isBool copilot-lua-cfg.panel.enabled) || copilot-lua-cfg.panel.enabled) ''
-        It is recommended to disable copilot's `panel` module, as it can interfere with completions
-        properly appearing in copilot-cmp.
-      '';
-
-    plugins.copilot-lua.enable = true;
-
-    extraConfigLua =
-      let
-        setupOptions =
-          with cfg;
-          {
-            inherit event;
-            fix_pairs = fixPairs;
-          }
-          // cfg.extraOptions;
-      in
-      ''
-        require('copilot_cmp').setup(${helpers.toLuaObject setupOptions})
-      '';
-  };
-}