FEATURE: Introduce site settings which require confirmation (#27315)

Many site settings can be distructive or have huge side-effects
for a site that the admin may not be aware of when changing it.

This commit introduces a `requires_confirmation` attribute that
can be added to any site setting. When it is true, a confirmation
dialog will open if that setting is changed in the admin UI,
optionally with a custom message that is defined in client.en.yml.

If the admin does not confirm, we reset the setting to its previous
clean value and do not save the new value.

spec/lib/site_setting_extension_spec.rb

@@ -892,6 +892,24 @@ RSpec.describe SiteSettingExtension do
     end
   end
 
+  describe "requires_confirmation settings" do
+    it "returns 'simple' for settings that require confirmation with 'simple' type" do
+      expect(
+        SiteSetting.all_settings.find { |s| s[:setting] == :min_password_length }[
+          :requires_confirmation
+        ],
+      ).to eq("simple")
+    end
+
+    it "returns nil for settings that do not require confirmation" do
+      expect(
+        SiteSetting.all_settings.find { |s| s[:setting] == :display_local_time_in_user_card }[
+          :requires_confirmation
+        ],
+      ).to eq(nil)
+    end
+  end
+
   describe "_map extension for list settings" do
     it "handles splitting group_list settings" do
       SiteSetting.personal_message_enabled_groups = "1|2"