CDK-742. Added logic to find cluster-provided Avro jars to CLI classpath

If we are going to call out specific jars, then I think there should be a work-around to turn that off (`$AVRO_JARS`?) in case things change.

For the check, I think we should just remove it. It doesn't currently guard anything. The alternative is to fail the setup if the directory isn't found, but that precludes users injecting a different avro version using KITE_CLASSPATH or other methods.