attributes: support extra value 'not applicable' for support (#75751)

* Support two extra values 'unknown' and 'not applicable' for support.

* Simplify to only one new state: 'n/a'

* Adhere to the IBM style guide.

test/lib/ansible_test/_util/controller/sanity/validate-modules/validate_modules/schema.py

@@ -542,7 +542,7 @@ def doc_schema(module_name, for_collection=False, deprecated_module=False):
             Schema({
                 any_string_types: {
                     Required('description'): Any(list_string_types, *string_types),
-                    Required('support'): Any('full', 'partial', 'none'),
+                    Required('support'): Any('full', 'partial', 'none', 'N/A'),
                     'details': Any(list_string_types, *string_types),
                     'version_added_collection': collection_name,
                     'version_added': version(for_collection=for_collection),