The ErrorsMethodArgumentResolver expects the preceding @ModelAttribute
in the controller method signature to be the last one added in the
model -- an assumption that can break if a model attribute is added
earlier (e.g. through a @ModelAttribute method) and more attributes
are added as well. This fix ensures when an @ModelAttribute is resolved
as a controller method argument it has the highest index in the model.
Issue: SPR-9378
Backport Issue: SPR-9687
4fccd1799a