DEV: Switch over category settings to new table - Part 3 (#20657)

In #20135 we prevented invalid inputs from being accepted in category setting form fields on the front-end. We didn't do anything on the back-end at that time, because we were still discussing which path we wanted to take. Eventually we decided we want to move this to a new CategorySetting model.

This PR moves the require_topic_approval and require_reply_approval from custom fields to the new CategorySetting model.

This PR is nearly identical to #20580, which migrated num_auto_bump_daily, but since these are slightly more sensitive, they are moved after the previous one is verified.

spec/models/category_spec.rb

@@ -906,22 +906,18 @@ RSpec.describe Category do
   describe "require topic/post approval" do
     fab!(:category) { Fabricate(:category_with_definition) }
 
-    describe "#require_topic_approval?" do
-      before do
-        category.custom_fields[Category::REQUIRE_TOPIC_APPROVAL] = true
-        category.save
-      end
+    it "delegates methods to category settings" do
+      expect(category).to delegate_method(:require_reply_approval).to(:category_setting)
+      expect(category).to delegate_method(:require_reply_approval=).with_arguments(true).to(
+        :category_setting,
+      )
+      expect(category).to delegate_method(:require_reply_approval?).to(:category_setting)
 
-      it { expect(category.reload.require_topic_approval?).to eq(true) }
-    end
-
-    describe "#require_reply_approval?" do
-      before do
-        category.custom_fields[Category::REQUIRE_REPLY_APPROVAL] = true
-        category.save
-      end
-
-      it { expect(category.reload.require_reply_approval?).to eq(true) }
+      expect(category).to delegate_method(:require_topic_approval).to(:category_setting)
+      expect(category).to delegate_method(:require_topic_approval=).with_arguments(true).to(
+        :category_setting,
+      )
+      expect(category).to delegate_method(:require_topic_approval?).to(:category_setting)
     end
   end