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/completion/helm/config.el

@@ -83,7 +83,7 @@ be negative.")
   :init
   (when (and EMACS26+ (featurep! +childframe))
     (setq helm-display-function #'+helm-posframe-display-fn)
-    (def-advice! +helm--fix-get-font-height-a (orig-fn position)
+    (defadvice! +helm--fix-get-font-height-a (orig-fn position)
       "Fix \"Specified window is not displaying the current buffer\" error."
       :around #'posframe--get-font-height
       (ignore-errors (funcall orig-fn position))))