Create example generator

This code adds a feature to the tests where all of the example
snippets are generated and then validated. Tests fail if the new
examples don't match the old ones, meaning a dev changing the API
must update the snippets, triggering a conversation about the changes
during the pull request.

Implements: blueprint example-snippet-generator
Change-Id: I5f1bfd47558a646a56e519614ae76a55759a4422
Merge "Create example generator"