MINOR: kafka system tests should support larger EBS volumes for newer instances (#12382)
MINOR: kafka system tests should support larger EBS volumes for newer instances (#12382)

When running with 4th generation instances supporting EBS only, we need
to use a larger volume or else we run out of  disk space during a system
test run.

This change also parameterizes the instance type as an env variable for
easier testing.

Reviewers: David Jacot <5fc0bbf1edd0c5fffb0c57f617de5d4a64ca0cc5@confluent.io>
guozhangwang/kafka,lindong28/kafka,apache/kafka,guozhangwang/kafka,lindong28/kafka,guozhangwang/kafka,lindong28/kafka,apache/kafka,apache/kafka,apache/kafka,guozhangwang/kafka,lindong28/kafka