Refactor Doom core init process (again)

- Eager-load all core autoloaded libraries if autoloads file isn't
  present.
- Renames functions to be more descriptive of their true purpose:
  - doom-initialize-autoloads -> doom-load-autoloads-file
  - doom-load-env-vars -> doom-load-envvars-file
- Use doom-module-p instead of featurep! for backend use (the latter is
  mainly syntax sugar for module use, and evaluates at compile/expansion
  time, which may cause hash-table-p errors early in the startup
  process).
- Reorder plist library to prevent load order race condition with the
  functions using the macros that haven't been defined yet.

core/core-cli.el

@@ -144,13 +144,6 @@ BODY will be run when this dispatcher is called."
 ;;
 ;;; Dispatch commands
 
-;; Eagerly load these libraries because this module may be loaded in a session
-;; that hasn't been fully initialized (where autoloads files haven't been
-;; generated or `load-path' populated).
-(load! "autoload/format")
-(load! "autoload/packages")
-
-
 ;; Load all of our subcommands
 (def-command! (refresh re) (&optional force-p)
   "Ensure Doom is properly set up.