💥 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/lang/org/config.el

@@ -803,9 +803,9 @@ compelling reason, so..."
        auto-fill-mode             ; hard line wrapping
        ;; `show-paren-mode' causes flickering with indentation margins made by
        ;; `org-indent-mode', so we turn off show-paren-mode altogether
-       doom|disable-show-paren-mode
+       doom-disable-show-paren-mode-h
        ;; Shows a lot of false positives, so...
-       doom|disable-show-trailing-whitespace
+       doom-disable-show-trailing-whitespace-h
 
        +org|enable-auto-reformat-tables
        +org|enable-auto-update-cookies