💥 Rename def-package! -> use-package!

Calling this pivotal macro "def-package!" has frequently been a source
of confusion. It is a thin wrapper around use-package, and it should be
obvious that it is so. For this reason, and to match the naming
convention used with other convenience macros/wrappers, it is now
use-package!.

Also changes def-package-hook! -> use-package-hook!

The old macros are now marked obsolete and will be removed when straight
integration is merged.

modules/lang/nix/config.el

@@ -1,6 +1,6 @@
 ;;; lang/nix/config.el -*- lexical-binding: t; -*-
 
-(def-package! nix-mode
+(use-package! nix-mode
   :mode "\\.nix\\'"
   :config
   (set-company-backend! 'nix-mode 'company-nixos-options)
@@ -16,11 +16,11 @@
         (:when (featurep! :completion helm)
           "o" #'helm-nixos-options)))
 
-(def-package! nix-drv-mode
+(use-package! nix-drv-mode
   :mode "\\.drv\\'")
 
-(def-package! nix-update
+(use-package! nix-update
   :commands nix-update-fetch)
 
-(def-package! nix-repl
+(use-package! nix-repl
   :commands nix-repl-show)