Introduce autodefs to replace some settings

+ :popup -> set-popup-rule!
+ :popups -> set-popup-rules!
+ :company-backend -> set-company-backend!
+ :evil-state -> set-evil-initial-state!

I am slowly phasing out the setting system (def-setting! and set!),
starting with these.

What are autodefs? These are functions that are always defined, whether
or not their respective modules are enabled. However, when their modules
are disabled, they are replaced with macros that no-op and don't
waste time evaluating their arguments.

The old set! function will still work, for a while.

modules/feature/file-templates/autoload.el

@@ -1,7 +1,7 @@
 ;;; feature/file-templates/autoload.el -*- lexical-binding: t; -*-
 
-;;;###autoload
-(def-setting! :file-template (pred &rest plist)
+;;;###autodef
+(defun set-file-template! (pred &rest plist)
   "Register a file template.
 
 PRED can either be a regexp string or a major mode symbol. PLIST may contain
@@ -24,11 +24,23 @@ these properties:
     file template rule against this buffer."
   `(push (list ,pred ,@plist) +file-templates-alist))
 
-;;;###autoload
-(def-setting! :file-templates (&rest templates)
+;;;###autodef
+(defun set-file-templates! (&rest templates)
   "Like `doom--set:file-template', but register many file templates at once."
   `(setq +file-templates-alist (append (list ,@templates) +file-templates-alist)))
 
+;; FIXME obsolete :file-template
+;;;###autoload
+(def-setting! :file-template (pred &rest plist)
+  :obsolete set-file-template!
+  `(set-file-template! ,pred ,@plist))
+
+;; FIXME obsolete :file-templates
+;;;###autoload
+(def-setting! :file-templates (&rest templates)
+  :obsolete set-file-templates!
+  `(set-file-templates! ,@templates))
+
 
 ;;
 ;; Library