list: factor out manual argument checking.

* lib/std/list.lua (depair, map_with, project, transpose)
(zip_with): Use new "container of thing" support in export type-
lists to replace manual checks.
(_ARGCHECK): Remove. No longer used.
* specs/list_spec.yaml (depair, map_with, project, transpose)
(zip_with): Adjust error expectations accordingly.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>