[1.7.x] Fixed #22087 -- Made AdminReadonlyField respect ModelForm Meta overrides.

Backport of 16afffffe8 from master

tests/admin_views/admin.py

@@ -35,7 +35,7 @@ from .models import (Article, Chapter, Child, Parent, Picture, Widget,
     UnchangeableObject, UserMessenger, Simple, Choice, ShortMessage, Telegram,
     FilteredManager, EmptyModelHidden, EmptyModelVisible, EmptyModelMixin,
     State, City, Restaurant, Worker, ParentWithDependentChildren,
-    DependentChild, StumpJoke)
+    DependentChild, StumpJoke, FieldOverridePost)
 
 
 def callable_year(dt_value):
@@ -435,6 +435,22 @@ class PostAdmin(admin.ModelAdmin):
     value.short_description = 'Value in $US'
 
 
+class FieldOverridePostForm(forms.ModelForm):
+    model = FieldOverridePost
+
+    class Meta:
+        help_texts = {
+            'posted': 'Overridden help text for the date',
+        }
+        labels = {
+            'public': 'Overridden public label',
+        }
+
+
+class FieldOverridePostAdmin(PostAdmin):
+    form = FieldOverridePostForm
+
+
 class CustomChangeList(ChangeList):
     def get_queryset(self, request):
         return self.root_queryset.filter(pk=9999)  # Does not exist
@@ -833,6 +849,7 @@ site.register(Recommender)
 site.register(Collector, CollectorAdmin)
 site.register(Category, CategoryAdmin)
 site.register(Post, PostAdmin)
+site.register(FieldOverridePost, FieldOverridePostAdmin)
 site.register(Gadget, GadgetAdmin)
 site.register(Villain)
 site.register(SuperVillain)