Move payee identifier widgets to kmm_widgets

Patch moves IBAN/BIC and national account number widgets from loadable to shareable, together with StyledItemDelegateForwarder which indirectly uses it. This makes payee identifier loader redundant and thus may allow to compile without --allow-multiple-definition linker option.
Redundant code will be removed after this patch gets accepted.

Differential Revision: https://phabricator.kde.org/D14540