refactor: clean up code to py39+ supported syntax
- f-strings instead of format
- latest typing support instead of pre 3.9 TitleCase
- remove UTF-8 declarations.
- many more changes
Powered by https://github.com/asottile/pyupgrade/ + manual cleanups
* The previously deleted code was being used in ERPNext's Customer
module.
* This will be moved into frappe.model.utils.rename_doc for the time
and completely removed in time.
