ConfigUpdater doesn't support basic config objects

Problem/Motivation

In #2656818: Implement optimistic locking for orders I tried importing a basic config object. The config importer died because it didn't detect it was a simple config entity.

Instead, the config type was null so it tried to load a null entity type definition and died.

Steps to reproduce

Try to import a basic config object

Proposed resolution

If the config type is null, assume it is a config object and write it using the config factory.

Remaining tasks

User interface changes

API changes

Data model changes