Replace 'Matchers' with 'CoreMatchers' So we do not require 'org.hamcrest:hamcrest-library' as additional dependency anymore. Which was only available for most of the tests because it leaked onto the test compile classpath.
Remove `getUsage` from `UsageContext` This `Usage` is an artifact of migration. `UsageContext` is mostly representing what an outgoing published variant is, but this `Usage` is preventing us from doing smarter things. What we really care about is the attributes of published variants, and their name for publication.