Add update testing using UpdatePathTestBase

Problem/Motivation

Thunder has lots of update hooks that add new functionality and configure things.

At the moment if you go from the tarball for 2.0 - https://www.drupal.org/project/thunder/releases/8.x-2.0 to latest Thunder release the update is not successful because module installs crash. This is because system_update_8400 does entity definition updates that result in schema changes.

Proposed resolution

Add code to thunder_update_dependencies() to ensure all thunder updates happen last and add an UpdatePathTestBase test.

In future Thunder could make more use of hook_post_update_NAME() to make updates to configuration etc as these always operate on a complete API.

Remaining tasks

User interface changes

None

API changes

None

Data model changes

None