Rename doom-before-switch-*-hook hooks

+ doom-before-switch-buffer-hook => doom-exit-buffer-hook
+ doom-before-switch-window-hook => doom-exit-window-hook
+ doom-after-switch-buffer-hook => doom-enter-buffer-hook
+ doom-after-switch-window-hook => doom-enter-window-hook

Shorter, easier-to-type names that better describe their intended
purpose.

The old names are still usable, but deprecated.

modules/ui/nav-flash/config.el

@@ -6,7 +6,7 @@
   ;; NOTE In :feature lookup `recenter' is hooked to a bunch of jumping
   ;; commands, which will trigger nav-flash.
   (add-hook!
-    '(doom-after-switch-window-hook
+    '(doom-enter-window-hook
       imenu-after-jump-hook evil-jumps-post-jump-hook
       counsel-grep-post-action-hook dumb-jump-after-jump-hook)
     #'+nav-flash/blink-cursor)