Locale should not use fetchObject with a classname, WSOD on sqlite

Problem

You cannot install Drupal 8 on sqlite and enable locale module. It whitescreens. The bug was introduced with new code in #1785086: Introduce a generic API for interface translation strings almost 2 months ago. Nobody noticed because people don't run tests (or Drupal 8 sites) on sqlite. In #1854752: Re-Add PDO::FETCH_PROPS_LATE to PDO::FETCH_CLASS Damien Tournoud suggests it is a foolish thing to use fetchObject() with a class name. It is not only that the core PHP implementation is broken, the PDO implementation is broken in a different way too.

Suggested solution

Grab the result set as an array and instantiate the object with that. This was suggested over in #1854752: Re-Add PDO::FETCH_PROPS_LATE to PDO::FETCH_CLASS by Damien.

The existing tests should already cover this extensively, but they did not fail before since obviously they run on MySQL and the PDO implementation did not have the same bugs as our PHP implementation has.