Refactor doom-debug-mode

+ Add explain-pause-mode
+ Now reloads itself if doom-debug-variables is changed or when one of
  its variables becomes available.
+ doom-debug-variables now supports a cons cell entry where its CAR is
  the name of the variable and CDR is the value it should be set to when
  doom-debug-mode is active.

modules/editor/snippets/config.el

@@ -33,6 +33,8 @@
              #'yas-minor-mode-on)
 
   :config
+  (add-to-list 'doom-debug-variables '(yas-verbosity . 3))
+
   ;; Allow private snippets in DOOMDIR/snippets
   (add-to-list 'yas-snippet-dirs '+snippets-dir)