(eshell-ls-orig-insert-directory): Remove.
(eshell-ls-unload-hook): Not a defcustom any more. Use advice-remove.
(eshell-ls-use-in-dired): Use advice-add/remove.
(eshell-ls--insert-directory): Rename from eshell-ls-insert-directory.
Add `orig-fun' arg for use in :around advice.
Make it check (redundantly) eshell-ls-use-in-dired.