Drops support for ViewEngine. Only projects using Ivy are supported. This shouldn't be a problem going forward, since Ivy is opt-in since ng9, and default since ng12 with ViewEngine support completely removed in ng13.
Removes ng-mocks as it doesn't work with angular > 13.0.2 yet, and it is not needed anyway. My decision is to use directive mocking as little as possible, in order to cover as much as I can with unit tests.
Prepares a migration guide and sets up links to legacy API docs
This PR: