New incremental lazy-loading at startup

This is for loading large packages (like org and magit) quietly in the
background during idle time. It is already set up to incrementally load
org and magit.

This is still experimental, however. the idle timers may need to be
tweaked.

modules/tools/magit/config.el

@@ -18,6 +18,8 @@ available.")
   :commands magit-file-delete
   :init
   (setq magit-auto-revert-mode nil)  ; we already use `global-auto-revert-mode'
+  (doom-load-packages-incrementally
+   '(dash f s with-editor git-commit package magit))
   :config
   (setq magit-completing-read-function
         (if (featurep! :completion ivy)