Parameterize Connect unit tests to remove code duplication

https://github.com/apache/kafka/pull/8722 added two new unit tests, WorkerWithTopicCreationTest and WorkerSourceTaskWithTopicCreationTest, that are almost complete clones of the existing WorkerTest and WorkerSourceTaskTest unit tests. There's a couple of comments (1, 2) in them about plans to parameterize the tests; we should do this sooner rather than later to avoid expending developer time on copy+pasting code changes across two tests when making modifications to the Worker and/or WorkerSourceTask classes.