Update transactions_test.py to support KIP-848’s group protocol config

This task is to update the test method(s) in transactions_test.py to support the group.protocol configuration introduced in KIP-848 by adding an optional group_protocol argument to the tests and matrixes.

See KAFKA-16231 as an example of how the test parameters can be changed.

The wrinkle here is that transactions_test.py  was not able to run as-is. That might deprioritize this until whatever is causing that is resolved.