FEATURE: Allow theme settings to request refresh (#15037)

Similar to site settings, adds support for `refresh` option to theme settings.

```yaml
super_feature_enabled:
  type: bool
  default: false
  refresh: true
```

lib/theme_settings_manager.rb

@@ -37,6 +37,10 @@ class ThemeSettingsManager
     @opts[:description] # Old method of specifying description. Is now overridden by locale file
   end
 
+  def requests_refresh?
+    @opts[:refresh]
+  end
+
   def value=(new_value)
     ensure_is_valid_value!(new_value)