Cleanup Angular file to avoid deprecation.
This replaces !64 (merged) which used a string for the callback. That technically should work but had never actually been tried... and an obscure bug in CiviCRM-core prevented it from working. As a workaround this moves the callback function to a class so the value of settingsFactory can be an array which is what core expects.
I've tested this patch now and it works & should be compatible with all versions of CiviCRM going back to 2020.