modules: move nixpkgs module to top-level modules

Make `pkgs` available to files submodules by passing _all_ module args
through. We already did this for `specialArgs`.

modules/misc/default.nix

@@ -3,7 +3,6 @@
     ./assertions.nix
     ./context.nix
     ./meta.nix
-    ./nixpkgs.nix
     ./nixvim-info.nix
   ];
 }

modules/misc/nixpkgs.nix

@@ -1,16 +0,0 @@
-{ defaultPkgs, lib, ... }:
-let
-  # TODO: https://github.com/nix-community/nixvim/issues/1784
-  finalPackage = defaultPkgs;
-in
-{
-  config = {
-    # We explicitly set the default override priority, so that we do not need
-    # to evaluate finalPkgs in case an override is placed on `_module.args.pkgs`.
-    # After all, to determine a definition priority, we need to evaluate `._type`,
-    # which is somewhat costly for Nixpkgs. With an explicit priority, we only
-    # evaluate the wrapper to find out that the priority is lower, and then we
-    # don't need to evaluate `finalPkgs`.
-    _module.args.pkgs = lib.mkOverride lib.modules.defaultOverridePriority finalPackage;
-  };
-}