Allow remote testing functionality w/ the embedded connect runtime

[orpiske]

Recently we switched to the same embedded Kafka connect runtime that is used by Kafka itself for their own testing.

Compared to the previous implementation we had, this increases the stability of our tests and ensure they mimic better what would happen in a real world deployment.

However, we still miss one feature from the the embedded Kafka connect runtime: the ability to point it to a remote Kafka instance instead of using the embedded one. This would allow us to increase the test matrix and cover the test with different Kafka versions, reproduce better other real world scenarios. It would also allow us to remove the code from the previous implementation and keep the test code clean.

A possible solution for this problem is to work with the Kafka community to add that feature to their embedded runtime.