modules: refactor module bootstrapping

Let's simplify things by defining all modules in `./plugins`, `./modules`
and `./wrappers/modules`.

Instead of currying `pkgs` into a bootstrapping module, we can require
`defaultPkgs` be provided as a special arg.

This refactor allows us to completely remove `flake-modules/modules.nix`!

modules/misc/nixvim-info.nix

@@ -0,0 +1,48 @@
+{ lib, ... }:
+with lib;
+{
+  # Attribute may contain the following fields:
+  #  - path: Path to the module, e.g. [ "plugins" "<name>" ]
+  #  - description: A short description of the plugin
+  #  - url: Url for the plugin
+  #
+  # We need to use an attrs instead of a submodule to handle the merge.
+  options.meta.nixvimInfo = mkOption {
+    type = (types.nullOr types.attrs) // {
+      # This will create an attrset of the form:
+      #
+      # { path.to.plugin.name = <info>; }
+      #
+      #
+      # Where <info> is an attrset of the form:
+      # {
+      #   file = "path";
+      #   description = null or "<DESCRIPTION>";
+      #   url = null or "<URL>";
+      # }
+      merge =
+        _: defs:
+        lib.foldl'
+          (
+            acc: def:
+            lib.recursiveUpdate acc (
+              setAttrByPath def.value.path {
+                inherit (def) file;
+                url = def.value.url or null;
+                description = def.value.description or null;
+              }
+            )
+          )
+          {
+            plugins = { };
+            colorschemes = { };
+          }
+          defs;
+    };
+    internal = true;
+    default = null;
+    description = ''
+      Nixvim related information on the module
+    '';
+  };
+}