def-advice!->defadvice! & conform to new advice conventions

This commit does two things:

- Renames def-advice! to defadvice!, in the spirit of naming convenience
  macros after the function/macro they enhance or replace.
- Correct the names of advice functions to indicate visibility and
  intent. A public advice function like doom-set-jump-a is meant to be
  used elsewhere. A private one like +dired--cleanup-header-line-a
  shouldn't -- it likely won't work anywhere but the function(s) it was
  made to advise.

modules/tools/gist/config.el

@@ -9,7 +9,7 @@
 
   (set-popup-rule! "^\\*gist-" :ignore t)
 
-  (def-advice! +gist-list-render-a (orig-fn &rest args)
+  (defadvice! +gist--open-in-popup-a (orig-fn &rest args)
     :around #'gist-list-render
     (funcall orig-fn (car args) t)
     (unless (cadr args)