Force autoloads to use absolute paths

Autoload paths used to be relative to arbitrary roots (usually
doom-modules-dir). This commit changes doom//reload-autoloads to iterate
over autoloads in doom-autoloads-file and replace their file paths with
an absolute one.

Theoretically this should make Emacs feel marginally faster, but we
*probably* get more of a benefit from a shorter load-path (because we no
longer need doom-modules-dirs, doom-core-dir or doom-psuedo-module-paths
in the load-path).

This is highly experimental however!

modules/config/private/init.el

@@ -12,7 +12,6 @@ Doom Emacs.")
   ;; `doom-initialize-packages' will treat `+private-config-path' as the root of
   ;; this module.
   (add-to-list 'doom-psuedo-module-dirs +private-config-path)
-  (add-to-list 'load-path +private-config-path)
 
   ;;
   (load (expand-file-name "init.el" +private-config-path)