feature/ivy: fix virtual buffers in +ivy/switch-workspace-buffer #331

The former +ivy/switch-workspace-buffer constructed its own collection
of buffers, so ivy-use-virtual-buffers would have no effect on it.  Use
internal-complete-buffer instead and ivy-read will know what to do under
the hood.

modules/completion/ivy/autoload/ivy.el

@@ -45,7 +45,8 @@
 If ARG (universal argument), open selection in other-window."
   (interactive "P")
   (ivy-read "Switch to workspace buffer: "
-            (mapcar #'buffer-name (delq (current-buffer) (doom-buffer-list)))
+            'internal-complete-buffer
+            :predicate #'+ivy--is-workspace-or-other-buffer-p
             :action (if arg
                         #'ivy--switch-buffer-other-window-action
                       #'ivy--switch-buffer-action)