Rewrite :defer semantics

:defer now supports a hook, a cons cell with (SYMBOL . INTEGER) where
SYMBOL is a hook and INTEGER is a number of idle seconds before the
package is autoloaded, or just the integer (as per the default behavior
of :defer).

Also fixes an issue where switch-buffer-deffered packages (like
smartparens) wouldn't load.

modules/completion/company/config.el

@@ -48,7 +48,7 @@ MODES should be one major-mode symbol or a list of them."
 
 (def-package! company
   :when (featurep! +auto)
-  :defer input
+  :defer pre-command-hook
   :config (setq company-idle-delay 0.2))