Officially deprecate ResourceDictField.iter*() functions.
Review Request #12643 — Created Sept. 25, 2022 and submitted
have been legacy for a long time, but with the removal of Python 2.7,
there's no longer any good reason to keep maintaining them.
This officially deprecates both. They will emit deprecation warnings on
use, recommending the modern replacements.
Other resource classes still have
ItemResource.iterfields(), for example), but there's no replacement
function available, and we may have to worry about names clashing. This
change is ignoring this situation, leaving it to another day to solve.
Unit tests pass.