Add opt-in rule to check for namespaced modules and plugins

[nkakouros]

Using modules with their simple name, e.g. copy, may be ambiguous now that collections have been introduced. A custom collection may have its own copy module and it could conflict with the one from the ansible.builtin collection. Adding such a rule would also help with tracking down unnamespaced modules/filters/etc and namespacing them in roles/playbooks/etc.