[web/form] Relax condition for non-translating field names we should test true condition instead of None, so if one raise a ValidationError using an empty string as 'no-field' marker instead of None, we don't get the PO file header that gettext likes to return when one attempt to translate an empty string.

Merge with 3.25 branch

[entities] Restore dc_ methods instead of __getattr__ proxy In 8de62610cea2, a __getattr__ proxy was introduced to handle compatibility with dc_* methods being called on entity instances instead of through the IDublinCore adapter. Unfortunately, __getattr__ does not play well with super() and since the latter is often used by, we here restore all dc_ methods with an explicit proxy to the adapter. More verbose but should work. Closes #17103999.