kafka_int_tests: cleanup delete_groups test

[rukai]

This PR cleans up the existing testing for kafka delete_groups:

• Previously there was an admin_cleanup function in the cpp driver modules that was hardcoded to the cpp driver.
  • this was leftover from the very earliest integration tests we had for kafka
  • This PR moves this logic into the higher level kafka_int_tests module, calling the new KafkaAdmin::delete_groups method
• Previously the java driver was untested, but this PR adds a delete_groups implementation for the java driver.
• Previously we ignored some failures in the cpp driver when deleting groups, I've not been able to reproduce those failures, so I just removed the extra handling.

[codspeed-hq]

CodSpeed Performance Report

Merging #1784 will not alter performance

_{Comparing rukai:cleanup_delete_groups_test (14db259) with main (421ec9e)}

Summary

✅ 38 untouched benchmarks