💥 revise hook/var fns naming convention (2/2)

This is second of three big naming convention changes. In this commit,
we change the naming conventions for hook functions and variable
functions:

1. Replace the bar | to indicate a hook function with a -h suffix, e.g.

     doom|init-ui -> doom-init-ui-h
     doom|run-local-var-hooks -> doom-run-local-var-hooks-h

2. And add a -fn suffix for functions meant to be set on variables,
   e.g.

     (setq magit-display-buffer-function #'+magit-display-buffer-fn)

See ccf327f8 for the reasoning behind these changes.

modules/term/vterm/config.el

@@ -7,7 +7,7 @@
   :config
   (set-popup-rule! "^vterm" :size 0.25 :vslot -4 :select t :quit nil :ttl 0)
 
-  (add-hook 'vterm-mode-hook #'doom|mark-buffer-as-real)
+  (add-hook 'vterm-mode-hook #'doom-mark-buffer-as-real-h)
   ;; Automatically kill buffer when vterm exits.
   (add-to-list 'vterm-exit-functions (lambda (buffer) (if buffer (kill-buffer buffer))))
   ;; Modeline serves no purpose in vterm