Refactor Beyond Identity integration factory

The following discussion from !153784 (merged) should be addressed:

• @.luke started a discussion: (+1 comment)

  Thought

  🤔 The :beyond_identity_integration factory is a bit unconventional. We normally define an integration factory to be project-level by default, and then pass the :instance trait to make it instance-level.

  We've defined it to be instance-level by default, and then pass instance: false to build non-instance level integrations. So we've introduced a kind of inverse logic for this one integration factory.

  Looking at our test suite, we often do want to build non-instance-level integrations in our tests, so I'm not sure if having the factory create an instance-level by default has much benefit. Having this one factory behave differently is a bit of a gotcha.

  It might be best to make it more conventional and have it be instance-level only when :instance trait is passed. This would be in a refactoring follow-up.