Ensure #reset_column_information clears child classes as well

I've added a redundant test for this under the attributes API as well,
as that also causes this bug to manifest through public API (and
demonstrates that calling `reset_column_information` on the child
classes would be insufficient)

Since children of a class should always share a table with their parent,
just reloading the schema from the cache should be sufficient here.
`reload_schema_from_cache` should probably become public and
`# :nodoc:`, but I'd rather avoid the git churn here.

Fixes #22057

activerecord/lib/active_record/model_schema.rb

@@ -339,6 +339,9 @@ module ActiveRecord
         @columns = nil
         @columns_hash = nil
         @attribute_names = nil
+        direct_descendants.each do |descendant|
+          descendant.send(:reload_schema_from_cache)
+        end
       end
 
       # Guesses the table name, but does not decorate it with prefix and suffix information.

activerecord/test/cases/attributes_test.rb

@@ -172,5 +172,18 @@ module ActiveRecord
         assert_equal int_range, klass.type_for_attribute("my_int_range")
       end
     end
+
+    test "attributes added after subclasses load are inherited" do
+      parent = Class.new(ActiveRecord::Base) do
+        self.table_name = "topics"
+      end
+
+      child = Class.new(parent)
+      child.new # => force a schema load
+
+      parent.attribute(:foo, Type::Value.new)
+
+      assert_equal(:bar, child.new(foo: :bar).foo)
+    end
   end
 end

activerecord/test/cases/persistence_test.rb

@@ -966,4 +966,16 @@ class PersistenceTest < ActiveRecord::TestCase
       widget.reset_column_information
     end
   end
+
+  def test_reset_column_information_resets_children
+    child = Class.new(Topic)
+    child.new # force schema to load
+
+    ActiveRecord::Base.connection.add_column(:topics, :foo, :string)
+    Topic.reset_column_information
+
+    assert_equal "bar", child.new(foo: :bar).foo
+  ensure
+    ActiveRecord::Base.connection.remove_column(:topics, :foo)
+  end
 end