Add further Twig template suggestions

Yeah I understand that from the themer perspective. Meanwhile the field is always attached to an entity.
So I think we should do it like fields to it typically. If we used an id or the fully loaded object should be decided based on the fact, if we already have the loaded entity there, so we don't cause extra load, if not.

Could you provide an example what's available for other (best core) fields? Also to find the best namings...

Updated the issue title and description.

So through $item->getEntity(); in viewElements, we can easily get the variation and the bundle, but the display mode is not that easy unfortunately...

@thomas.frobieter, would that suffice? We could also pass any other variation variables if needed!