Allow te set a display label per quiz type

Problem/Motivation

You can configure the display label for the quiz entity type. This functionality is currently broken.

Also, this label is used for all quiz bundles. It would be a nice feature if you could configure this per quiz type/bundle.

Proposed resolution

Store the display label in the quiz type config entity.

Remaining tasks

User interface changes

The quiz type display label setting is moved from Admin > Quiz > Settings to Admin > Quiz > Structure > Quiz Types > Edit quiz type

API changes

Data model changes