Fixed #32316 -- Deferred accessing __file__.

Deferred accessing the module-global variable __file__ because the
Python import API does not guarantee it always exists—in particular, it
does not exist in certain "frozen" environments. The following changes
advanced this goal.

Thanks to Carlton Gibson, Tom Forbes, Mariusz Felisiak, and Shreyas
Ravi for review and feedback.

django/forms/renderers.py

@@ -7,8 +7,6 @@ from django.template.loader import get_template
 from django.utils.functional import cached_property
 from django.utils.module_loading import import_string
 
-ROOT = Path(__file__).parent
-
 
 @functools.lru_cache()
 def get_default_renderer():
@@ -33,7 +31,7 @@ class EngineMixin:
     def engine(self):
         return self.backend({
             'APP_DIRS': True,
-            'DIRS': [ROOT / self.backend.app_dirname],
+            'DIRS': [Path(__file__).parent / self.backend.app_dirname],
             'NAME': 'djangoforms',
             'OPTIONS': {},
         })