Views helper fails to return translated field values

Problem/Motivation

Currently EntityFieldHandlerHelper doesn't define a language in the methods that fetch values from the wrapper.
But the default handling of the entity wrappers seems somewhat bogus. There are cases in which the set language is NULL, leading to a fallback handling even though the global language is properly set.

Proposed resolution

Prime the language for wrapper instances of EntityStructureWrapper in the methods EntityFieldHandlerHelper before fetching the values.
Attention this relies on #2335885: 'langcode' option in info array is not applied to work properly, since otherwise the set language doesn't seem to bubble up from the property to the parent when fetching the data from the parent.

Remaining tasks

User interface changes

API changes

Data model changes