fix: #3603015 Hide disabled sub-properties of address elements

The webform_address items producer returned every non-empty sub-property, exposing ones denied by #access while every other composite filtered them through the WebformElements walker. Extract the access check into WebformElementAccessTrait and apply it in both walkers so a disabled sub-property (e.g. #state_province__access: false) is omitted from items.

Closes #3603015