refactor: move `list.shape` to `table.shape`.

* specs/table_spec.yaml (shape): Specify full behaviours.
* specs/list_spec.yaml (shape): Specify deprecation warnings.
* lib/std/list.lua (shape): Move from here...
* lib/std/table.lua (shape): ...to here.
* NEWS: Update.

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