* Add test to ensure macro call `::core`-related functions
Avoiding local core modules to break the macro-generated code.
Currently failing due to issue with `EnumIter` macros.
* Fix macro of `EnumIter`
close https://github.com/Peternator7/strum/issues/284
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Co-authored-by: kraktus <kraktus@users.noreply.github.com>