Update type annotations for `pax_fiddle.sub_field` and `pax_fiddle.template_field` to appease pytype.  Without this update, pytype complains if you use these field declarations.  E.g.:
Update type annotations for `pax_fiddle.sub_field` and `pax_fiddle.template_field` to appease pytype.  Without this update, pytype complains if you use these field declarations.  E.g.:

> praxis/pax_fiddle_test.py:37 in Vehicle: Type annotation for owner does not
> match type of assignment [annotation-type-mismatch]
>   Annotation: Person
>   Assignment: dataclasses.Field

PiperOrigin-RevId: 476185623

google/praxis,google/praxis