modules/keymap: improve lua deprecation

- Replace nullable lua option with a no-default option.
- Made it so the deprecated option is only declared when `lua = true` is passed.
- Replace `normalizeMappings` with a `removeDeprecatedMapAttrs` helper.
- Added warnings for all options that historically had `lua` support.

plugins/utils/tmux-navigator.nix

@@ -179,8 +179,10 @@ helpers.vim-plugin.mkVimPlugin config {
             ];
             example = "left";
           };
+          lua = true;
         }
       );
+      apply = map helpers.keymaps.removeDeprecatedMapAttrs;
     };
   };