Fixed #33366 -- Fixed case handling with swappable setting detection in migrations autodetector.

The migration framework uniquely identifies models by case insensitive
labels composed of their app label and model names and so does the app
registry in most of its methods (e.g. AppConfig.get_model) but it
wasn't the case for get_swappable_settings_name() until this change.

This likely slipped under the radar for so long and only regressed in
b9df2b74b9 because prior to the changes
related to the usage of model states instead of rendered models in the
auto-detector the exact value settings value was never going through a
case folding hoop.

Thanks Andrew Chen Wang for the report and Keryn Knight for the
investigation.

docs/releases/4.0.1.txt

@@ -19,3 +19,7 @@ Bugfixes
 * Relaxed the check added in Django 4.0 to reallow use of a duck-typed
   ``HttpRequest`` in ``django.views.decorators.cache.cache_control()`` and
   ``never_cache()`` decorators (:ticket:`33350`).
+
+* Fixed a regression in Django 4.0 that caused creating bogus migrations for
+  models that reference swappable models such as ``auth.User``
+  (:ticket:`33366`).